Nice to have you in the Community. I'd be glad to lend a hand with the Banking tab not opening.
There haven't been other reports of users not being able to get the Banking tab to open. Generally, when a user encounters unexpected behavior in QuickBooks Online, such as pages not loading, it's recommended to try browser troubleshooting.
If you haven't tried clearing your browser's cache, I recommend doing that and then seeing if the Banking tab will load. Cache is stored in order to speed up loading times, however, too much can accumulate and impede processes. I'm including an article that includes the steps for each supported browser: Delete Or Disable Cache And Temporary Internet Files In Your Web Browser.
Should you continue to experience issues with the Banking tab, you may wish to try another supported browser. This can help to isolate the cause of this behavior.
This should help to get you back on track and access to the Banking tab.
Don't hesitate to let me know if you should need anything else. Wishing you well.