Before digging deeper into your concern, we'd like to ask what bank account you're attempting to connect to your QuickBooks Online (QBO) company. A possible reason you can't link it to your QBO account is that there are ongoing maintenance or updates on your bank's end. That said, you'll want to check their official website to determine if they're updating their system.
If there's a notification, you'll want to contact our Customer Care Team so they can access your account in a secure environment and conduct further investigation to determine why you can't connect with your bank. We'll write down the steps to get you going:
In your QuickBooks Online company, select (?) Help.
Select either tab to get started:
Assistant: Get quick, personalised answers. Select a suggested option, or type a question or topic you need help with. If you decide you need further help, you can still chat to a human.
Search: Type a question, keyword or topic for QuickBooks Online self-help content or select Contact Us, type a question and Continue. Choose Start a chat with a QuickBooks support expert online.
If you need assistance managing a bank connected to QuickBooks, or if you have other tasks you'd like to complete inside the program. We'll be happy to help you out again. Don't hesitate to comment below. Stay safe, and have a good one!