Thanks for bringing this to our attention here in the Community, @Anonymous.
This time, we have an open investigation about the error you're getting when trying to update your Barclays bank feeds. Our banking engineers are actively working to have a permanent fix.
As an alternative, you can use the WebConnect process. This way, you can bring in all the transactions into the program.
You'll first download a .CSV file from your bank's website. Here's how:
Once done, you can upload the file into the system by performing the steps below:
I'm including this helpful article to serve as your reference: WebConnect or Bank Transaction Upload.
In line with the ongoing investigation, it'll be best to reach out to our QuickBooks Online Customer Support Team. By doing so, they can add your account to the list of affected companies. Also, they'll be able to notify you about the issue's status via email.
We thank you for your patience, @Anonymous. I'll be around to help if you have other online banking concerns. Stay positive always.
So the issue isn't fixed - yet despite this, I get support emails saying that:
"Dear Valued QuickBooks Online Customer,
Our engineers were under the impression that this was resolved, however we have now had reports that the account balance is updating, but no transactions are coming through. The engineers have reopened the investigation and are working as quickly as they resolve this. As they are working on this under the same investigation, you will still receive updates on when this is resolved.