Plex no longer works on Armstrong Tivo cable box as of 09/30/2021

Hi Dave, the problem you are experiencing is described here: Important information about Plex for smart TVs after September 30, 2021

HOWEVER the fix they give does not work on Tivo boxes. You have to set secure connections to “Disabled” on the server for it to work as well as turning off security on the Plex app on the Tivo device as described in the link article.