These issues should be resolved as they occur in the year of the account owner's death per Revenue Ruling 84-73, not handled en masse when they have accumulated.
As you know the decedent's TIN is no longer valid, you can remove it from the account. Now, you have an account without a valid TIN so backup withholding is required. The co-owners will appear.
This isn't the first thing you do, but it is what you do when they have not responded to prior requests.