What is remedy for Error 377 when trying to bank?

We can manually update your banking, prh3661.

The error 377 means that there is a connection issue between your bank and QuickBooks Online. Updating it can reestablish the connection to help download those transactions without any errors.

You'll see the Update Now link on the Banking page. Click it and wait for it to load.

Also, you'll want to read this article about uploading manually transactions into QuickBooks Online.

I'm looking forward to assisting you again.