When I tap the app, it immediately crashes. I don't want to delete and reinstall the app because I am scared to lose my tokens.
You have to reinstall the application without deleting it:
- Go to Settings > iPhone Storage
- Find Authenticator
- Tap "Offload App"
- After the process tap "Re-install App"
This provides to remove and install the application part, not your data/tokens. Your data remains.
I tried and succeeded on iPhone XS iOS 14.2.
If you want to be sure that you always have a backup of your 2FA accounts, I would suggest the use of Authy
It also enable you to have 2FA accounts across other devices - e.g. iPhone, iPad, Mac, Android, Linus and Windows - they are always in sync, and if you get a new device, you just login, and you are up and running.