CERT: incomplete TLS handshake: sslv3 alert certificate unknown

[FordGuy61]

@tjhole

Server Version#: Version 4.12.3 (Synology native Package)
Player Version#: Android/TV

Verify your Plex Media Server version. It will be 1.x, not 4.x.
Settings → Server_Name → General
or Authorized Devices

Synology model?

The Plex Media Server version provided by Synology is out of date. If you are using that version, download a current version from plex.tv and perform a manual update.

If you are running an old version of PMS, you are probably running into this problem:

Connection Error when playing films on android tv app

As @richyh67 mentions, there is a problem with current versions of Android/Android TV apps and older versions of Plex Media Server. The Android apps are rejecting the security certificate from the server for some reason. Users running Plex Media Server versions 1.18.x and 1.19.x are definitely affected. The problem may happen with other Plex Media Server versions (I don’t have a list of all affected releases). The problem is visible in the Android client log: [FFmpeg] [ERROR] [tls @ 0xc35efb…