Thank you for posting in the Community. Let me give you information about missing transactions in QuickBooks Online.
If part of your banking feeds is missing, then you'll have to manually update the transactions on the banking page.
Let me show you how to update the transactions:
From the left pane, select the Banking or Transactions menu.
Select the Banking tab.
Select the account you’re working on.
Then, click on the Update button.
Also, you can manually upload transactions into QuickBooks Online. Once done, you can categorize and match the transactions to make sure that everything is uploaded.