May I know the specific bank you're having problems with and isn't it updating automatically? I'd appreciate it if you can elaborate more about this so I can provide you the best route to resolve the issue.
In the meantime, you can try to manually update your bank feeds, and see if it downloads your bank transactions. You can follow the steps below for the process:
Go to the Banking menu from the left navigation panel.
Select the Banking tab.
Choose the bank account you're having problems with under the Bank and Credit Cards section.
Click the Update button.
Once done, if the transactions aren't still downloading. I suggest to manually download your bank transactions from your bank's website and import them into QuickBooks using a Webconnect file.