Error: will neither update nor re-install Mobile Security & Antivirus

Received update message today. Tried to update and received error message- “Mobile Security & Antivirus” could not be downloaded due to an error. (Error retrieving information from server. [RPC:S-2:AEC-2]) Uninstalled. Now I cannot re-install.
Have tried to download via Verizon and three Wi-Fi hotspots. Moto-X 2nd Gen.

See: https://forum.avast.com/index.php?topic=160110.0