Please know that this isn't the type of service we want you to experience. Allow me to join this conversation and provide information about this concern.
This issue only occurs when you delete a COA account from the Chart of account page without ticking the box to disconnect your bank. That's why your QuickBooks still detect your bank account connected.
To resolve this, you can use WebConnect or Express WebConnect as long as QuickBooks Online supports the file type. You can check this article for more information about the importing transactions with its file format: Manually upload transactions into QuickBooks Online.
Also, you can check this article about troubleshooting bank feeds web connect import issues and errors: Troubleshoot Bank Feeds Web Connect import issues and errors.
Please let me know if you need anything else.