Thanks for reaching out in the Community! I'd be happy to provide some information on troubleshooting your mobile app and bank connection issues.
When the application is not fully functional, one of the causes is the app's data. To isolate this, let's reset it. This process plays the same role as clearing the cache from your web browser. Please refer to the steps below.
In your Phone Settings:
From your phone's settings, tap Apps (varies by device). Choose the QuickBooks app from the list and select Storage. Select clear data.
Once done, restart your device and reopen your QBO mobile app to double-check.
For bank connection errors, What is the exact error message you are getting when trying to link your bank in your QuickBooks app? This way, we can review if there's an ongoing investigation or provide you with the right solution.