I edited my reply to remove POA; once you are dead, there is no POA for you.

Someone is "getting the mail" and that's where I start. Someone is the beneficiary, someone is a surviving heir, someone has to notify SS that the person has died, to stop the payments. Someone had access to the banking, or at least, to the banker.

"But, regardless, wouldn't personal rep be adequate to file as if Mom was filing?"

Is this a different question? I thought the question had to do with a deceased person.

"Personal Representative" means different things. POA, guardianship, executor, etc, all mean different things.