Let me help you connect your bank to QuickBooks Online.
May I know what financial institution you're using for online banking? Also, did you get any error messages or codes when connecting your bank? Any details about the issue will help us narrow things down.
In the meantime, let's try troubleshooting this unexpected behavior by updating your bank manually. Here's how you can do that:
Go to the Banking menu.
Click the Banking tab.
Select the account you'd like to update.
Click the Update button at the upper right corner.