Try to check with your bank how they send your bank transactions to your QuickBooks Online (QBO) account. From here, create a parent and then subaccounts. Check this article for more information: About bank or credit card subaccount setup.
In the meantime, you can manually download the transactions from the bank and then upload the file to your account.
To do this, go to your online banking account and get a copy of your transactions. Once done, go back to your QBO account and upload or import the transaction from there. See this article for more information: Manually upload transactions into QuickBooks Online.
Let me know if there's anything that I can help with your transactions. I'm always here to assist.