This can happen if you have automatically created Azure Resource Manager Connections using the DevOps GUI - the entra credentials, by default, only last for 3 months. To make matters worse, you won't be able to create a new service connection with the default settings because the name contains the subscription ID, and has to be unique.

Instead, select the Azure subscription instead of the Service Connection, but instead of clicking Authorize, hit the drop down to open advanced settings and set a unique name of the new service connection. You can then pick this one from the service connections last