Thank you for the reports of this issue - we’re working on a fix right now and hope to have an update in the store later today. We’re so sorry for the inconvenience!
The issue is related to biometrics - if anyone fancies trying to see if they can work around it, resetting your biometrics in Android’s Settings may help. Remove all your fingerprints from your device, and then re-add them. We would be interested to hear if this proves successful 
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Same problem here, Google Pixel 9 Pro, Android 15 - app launches then closes immediately
Please can Monzo email to their customers that they are aware of the issue and approx time scale for a fix. Thank you!
They won’t be emailing but they are hoping for a fix today.
App version 6.6.1 is now available with a fix. Sorry again for the trouble!
Just lost some money i transferred from another account into monzo. There’s no sign of this transaction.
Never happened before. This amount was to pay for an outgoing bill tomorrow.