Troubleshooting

This page helps you resolve the most common issues you’ll hit while scanning at the door. Each section follows a problem → solution structure. For the detail of any specific scan result, open the Scan states reference.

Tip

Golden rule: when the scanner shows a red error, do not admit the guest — read the on-screen message and follow it. When it shows amber, the issue is usually temporary; you can wait or switch doors.

Common problems

1. “Session expired” / kicked out

Your sign-in session has expired or been invalidated — usually because you signed in on another device or your permissions were re-issued.

1. Dismiss the error screen

   Tap “Sign in again”, or reload the Scanner page.

2. Sign back in

   Use your credentials or QR sign-in code as described in Sign in to the scanner.

3. Re-select the event and door

   After signing in, choose your event and door again. Any pending scans are still safe on the device and will sync when the network returns.

Note

A session-expired error is an input error, so the system does not queue it offline. You must sign back in before you can keep scanning — this is the correct behavior and avoids an error loop.

2. Network lost / network error

When the network drops, the system automatically caches successful scans and shows a “queued locally” message (amber). Only a retry that still fails reports a network error (red).

Amber screen (queued locally)

• The scanner is offline and the check-in has been cached safely.
• Keep scanning as normal — nothing to change.
• Reassure the guest: “Your ticket scanned fine, it’s syncing.”
• When the network returns, the system syncs everything in the correct time order.

Red screen (network error)

• Transient network failure, the server can’t be reached.
• Retry that ticket.
• If failures persist, subsequent scans fall back to the offline queue (amber) automatically.
• Check Wi-Fi/4G; if the device has no signal at all, just keep scanning — your data is safe.

Tip

Each cached scan carries an accurate timestamp from the moment you scanned, so the check-in order on the server is always correct regardless of when the network recovers. See Scanning offline for the detail.

3. Can’t sign in to the Scanner

Symptom	Cause	Fix
Wrong username / password	Typo or forgotten	Ask the organizer to reset your password.
Account has no scanning rights	Not assigned the door-staff role	Contact the organizer to grant event/door access.
QR sign-in code won’t scan	Code expired or used on another device	Ask the organizer for a fresh QR code.
No events visible to scan	Event isn’t assigned to you	Ask the organizer to assign the event + door to your account.

Note

Scanner accounts must be pre-authorized by the organizer in the admin dashboard. If you see no events or doors after signing in, that’s a permissions issue — contact the organizer, it isn’t an app bug.

4. Guest says “I’ve already scanned” but needs back in

This splits by whether the event has check-out enabled or is single-entry only.

Event WITH check-out enabled

• Re-scanning a guest who is inside auto-checks them out (blue screen).
• The next scan checks them back in — guests can come and go.
• You don’t need to do anything extra; just let the guest know they’re handled.

Event WITHOUT check-out (single entry)

• Re-scanning shows yellow with the previous check-in time + door.
• Under the default policy, do not admit them again.
• If it’s a genuine edge case (guest stepped out by mistake), contact the organizer to undo the check-in manually from the admin dashboard.

Caution

Door staff cannot undo a check-in from the Scanner. Only an organizer can do this from the admin dashboard.

5. Door reports full

The door has reached its configured capacity.

• Redirect the guest to another door that still has space.
• Or wait for a check-out to free a slot.
• If you think the capacity is misconfigured, contact the organizer to check the door’s capacity setting.

6. Time window closed / not open yet

Check-in closed (after check-in hours)

• The current time is past the check-in end.
• Ask the organizer to extend the window (check-in end time) in the admin dashboard.
• Once extended, scanning will succeed.

Check-in not open yet (before check-in hours)

• The current time is before the check-in start.
• Ask guests to wait until opening time.
• If the opening time is wrong, ask the organizer to fix the check-in start time.

Day not enabled (multi-day event)

• The event has a daily schedule but today isn’t an enabled day.
• Check the schedule with the organizer — the guest may have come on the wrong day.

7. Camera not working / permission denied

The scanner can’t open the camera — most common on iPhone using Safari. There are three separate situations, each with a different fix.

Dismissed once (permission prompt visible)

• The browser just asked “Allow camera access?” and you haven’t tapped Allow yet.
• Tap Enable camera on the screen to request permission again.
• If the prompt no longer appears, see “Permanently denied” below.

Permanently denied (camera-off screen)

• You previously chose Don’t Allow, so the browser remembers and stops asking.
• You must open the device/browser settings and re-enable the camera:
  • iPhone + Safari: Settings → Safari → Camera → Allow.
  • iPhone + Chrome: Settings → Chrome → Camera → Allow.
  • Android + Chrome: Settings → Apps → Chrome → Permissions → Camera → Allow.
  • Desktop: Browser settings → Site settings → Camera → Allow.
• After enabling, return to the scanner and tap Try again.
• Tip: on iPhone Safari you can also use the aA button in the address bar → Website settings → Camera → Allow.

Insecure address

• The camera only runs on a secure connection (look for the padlock in the address bar). If you opened the page over a plain, non-secure address, the camera can’t start.
• Make sure you open the scanner page at portal.qrs.com.vn.

Tip

If the camera still won’t open after granting permission (or the device has a broken camera), switch to manual entry or use an external barcode scanner — see the next two sections. You don’t have to fix the camera to keep checking guests in.

8. Using an external barcode scanner (USB/Bluetooth)

An external barcode scanner — a handheld scanner plugged in via USB or paired over Bluetooth — works just like a keyboard: it scans the code, types the character string, and submits it automatically. You don’t need to install anything, and you don’t need to turn on the camera.

1. Plug in or pair the device

   USB: plug into a USB port on your computer/tablet. Bluetooth: pair following the scanner’s instructions.

2. Place the cursor in the ticket code field

   On the scanner screen, open the manual ticket code entry field and tap the input box so the cursor appears.

3. Scan the ticket

   Aim the scanner at the ticket code. The string is typed into the box automatically and submitted — the result shows exactly like a camera scan.

Note

Because an external scanner types like a keyboard, it does not need browser camera permission. This is a reliable fallback when a phone camera won’t work, or when you’re using a desktop computer without a camera.

9. Another device took over my session

There are two different messages, both of which take you back to the sign-in screen:

'Session taken over' screen (amber)

• Another device signed in with the same account and took over this scanner session.
• This is by design: each account keeps only one active scanner session at a time, so two people can’t scan duplicate check-ins on the same account.
• Sign in again to reclaim the session, or scan the QR sign-in code issued by the organizer.
• Pending scans already on the device are still safe and will sync when the network returns.

'Session expired' screen (red)

• The session has timed out, or your account permissions were just re-issued.
• Tap Sign in again or Scan QR code to return to the scanner.

Note

A session-expired error is an input error, so the system does not queue it offline. You must sign back in before you can keep scanning. Successfully scanned check-ins from before are still saved — just sign back in to continue.

Less common errors

State	Color	Quick fix
Invalid QR	🔴 Red	QR not in the system. Use manual lookup (the “No Ticket” button) if the guest has an account.
Invalid ticket	🔴 Red	Ticket expired or revoked. Direct the guest to the organizer.
Wrong event	🔴 Red	Ticket belongs to another event. Redirect the guest to the right event.
Ticket tier not allowed at this door	🔴 Red	Tier not allowed at this door. Direct the guest to an allowed door.
Door inactive / Event inactive	🟠 Amber	Door or event deactivated. Contact the organizer.

Frequently asked questions (FAQ)

A scan succeeded but I don’t see it in the admin dashboard? If the scanner is offline, the scan is in the local queue. When the network returns and Pending reaches 0, it will appear in the admin dashboard. Watch the Online / Pending counters in the scanner header.

Does a power loss wipe my pending scans? No. Scans are stored on the device, not in volatile memory. Reopening the app (same device, same profile) keeps them intact.

The ticket scanned but the guest’s name is wrong? The name, event, and tier come from the e-ticket record. Ask the organizer to fix the guest’s details in the admin dashboard — you can’t edit it at the Scanner.

Do I need to tap “Sync” manually when the network returns? No. Sync is fully automatic. Just keep working the door.

The guest lost their phone and has no QR ticket? Use the “No Ticket” button in the Scanner to search by name/email and check them in manually (requires an active ticket). See Special cases.

Learn more

Scan states referenceThe full table of all 14 scan states with colors and actions.

Edge casesRare situations and how to handle them in detail.

Scanning offlineDetail on the offline queue and automatic sync.

Special cases at the doorManual lookup, duplicate scans, and other door situations.

Back to Event Check-in overviewReturn to the overview page.