I have all the steps you'll need to fix bank connectivity issues in QuickBooks Online.
Before we start, may I ask the name of your bank to verify and check any open investigation?
If you didn't receive any error messages, you can try signing in to your bank’s website to check if everything is working on their end. Then, manually update your bank connection to get the latest available transactions.
Select Banking or Transactions from the sidebar menu.
Go to the Banking tab.
Choose the appropriate bank account.
If the issue persists, let's reconnect your account using a private browser to help us determine if this is a browser-related issue. To access QuickBooks using incognito, you may use either of these shortcut keys:
Google Chrome, press CTRL + Shift + N
Mozilla Firefox: press CTRL + Shift + P
Safari: press Command + Shift + N
Once you're in, head to the Banking or Transactions menu again. If you're able to connect without any issues, go back to your regular browser and then clear its cache and cookies to start over fresh. Alternatively, you can switch to other supported browsers.
Here are some articles that help ensure accounts are matched and accurate. Visit them moving forward for detailed instructions: