How1 I've just installed two banking apps and they're no longer working. Up until now they've been fine.
I do not understand - did you reinstall the apps or have you switched to GrapheneOS from different OS?
Anyway, GrapheneOS has some limitations when it comes to banking apps:
Banking apps are increasingly using Google's SafetyNet attestation service to check the integrity and certification status of the operating system. GrapheneOS passes the basicIntegrity check but isn't certified by Google so it fails the ctsProfileMatch check