@versydney Thanks for posting your question in Microsoft Fabric Community
If the Fabric notebook was working yesterday and is not working today, it is possible that there was a change in the configuration or environment that is causing the issue. The error message suggests that you need to provide either a connection string or an account name with credentials to access the data source There could be several reasons why this error occurred. One possibility is that the credentials you used to access the data source have expired or are no longer valid.
This could also be an intermittent issue. I would also suggest trying again later in the day to see it the issue still persists.