There is an issue they are working to resolve. You may have received an email a short while ago announcing the situation. They have sent a n update.

"Some customers are receiving an error when attempting to update their bank connection. Error: 'Something's not quite right...'

Incident status: Identified

Some customers are currently unable to update their bank accounts in QuickBooks Online. We’ve identified the source of the problem and are working to resolve the issue."

Jul 19, 09:59 PDT