There is a problem with current Android TV clients and older versions of Plex Media Server.
1.18 and 1.19 are definitely affected. I do not know if 1.20.1 is affected.
The workaround is to disable secure communications between the client and server.
Updating to a current PMS release solves the problem. Note that 1.20.1 was released in Aug 2020. You may wish to update to a current release (1.24.2.4973). There are many enhancements and bug fixes (see release notes).
This post has additional details, including how to tell if you’re running into the same issues as people on 1.18 & 1.19 (you have to look at the Android TV log file):
