I appreciate the things you've done to ensure that the bank feeds work again. Since you've already updated the credentials of your bank account, you can try clicking the Update button again.
If you're getting an error after clicking this, you may want to share it with us so that we can assist you further. However, if you're not getting any errors and the bank transactions are also not updated, I'd recommend contacting our QuickBooks Online Care Team to help you get back on track.
For now, I'd recommend manually uploading your transactions from your bank to QuickBooks Online. Here's how:
Log in to your bank's website and download the bank transactions using the .CSV file.
Sign in to QuickBooks and go to Transaction menu.
Select the account and click Upload from file.
Follow the on-screen instructions. You can refer to the screenshot below: