Let's get your online bank account to work without any issues.
Before we proceed further, I'd appreciate it if you can provide additional information on your issue. If you see any error codes or error messages when you click the Update button, it would help resolve this problem.
At this time, what I can suggest is to check if you're able to log in to your actual online bank's web page. From there, check for any messages, notifications, or alerts. These can block QuickBooks Online (QBO) from downloading your bank transactions.