I recognized how important it is to have your bank transactions sync with your QuickBooks Online (QBO) account. I'd like to help and get you back in working order. Can you share with me the name of your bank? This way, I can check here on my end if there is any related issue. Any additional information is appreciated.
Also, I'd recommend reaching out to your bank and verify if there’s an issue or maintenance update on their end. Thus, it could be the reason why you’re missing four months of your bank transactions.
In the meantime, let’s manually download your bank transactions to your account. Let me guide you how:
Go to the Banking or Transactions menu.
Select your bank account and click Update a couple of times to refresh the connection between your bank and QBO.
If asked, enter your Multi-Factor Authentication (MFA) credentials. Then select Continue update.