Welcome to the Community, Mark!
Can I ask the name of the bank account connected on file? This way we can check if there is any reported product investigation with your bank.
QuickBooks Online (QBO) automatically downloads your bank transactions when you link your account. However, the imported information depends on your bank's data. If there are missing transactions, you can download a CSV file from your bank and manually upload it. Or manually create the missing transaction in QBO through the + New option.
Furthermore, let's check the Categorised and Excluded tab to make sure the transaction was not added or removed in QBO.
Check out this link for further information about manually uploading data to QBO: Manually upload your transactions, receipts, and bills into QuickBooks Online.
If your bank feeds is connected through Direct feeds, they are send to QBO weeknight. Check this link to learn more about the scheduled download of your bank feeds: Direct bank connections with QuickBooks Online | FAQ.
Post again in the Community if you have other questions about QBO.
