The bank error you have encountered means QuickBooks can't connect to your bank. You can follow these steps to update your bank connection and sync your transactions:
Go to All Apps, then select Accounting.
Choose Bank transactions.
Click the Update button.
If you still see an error, please wait for 2 to 3 hours and try again.
However, if the issue persists after trying, please visit your bank's website to check for any maintenance or technical issues that may be causing the error.