Account access by two ATT STBs

On Sunday March 31, 2019, I watched and recorded several programs with my ATT Motorola UVerse STB/DVR which is connected to my TV.

On Monday April 1, 2019, I attempted to continue watching one of the programs, using the same ATT Uverse equipment described above.

Instead of being able to view the saved programs on the existing ATT Uverse STB/DVR, I received the following 2 line error message on the TV after starting the STB/DVR with the ATT Uverse remote control:

"Account unavailable.      Restart Receiver 

This Set Top Box does not match the account settings"

On April 1, 2019, I replaced the ATT Uverse Motorolla STB/DVR with a Cisco STB/DVR, sent to me, to resolve unrelated issues, on March 1, 2019.

After configuration, and restarting the Cisco STB/DVR, I received the 2 line error message, again.

"Account unavailable.      Restart Receiver 

This Set Top Box does not match the account settings"

I chatted with ATT online Support, did troubleshooting with their guidance, and was not able to resolve this issue for the Cisco STB/DVR.  The support person is sending a newer Cisco Advanced STB/DVR.

I wonder if there is a step that can be taken for resetting the existing Cisco STB/DVR ?