fix PLEX IPTV

I'm looking to hire a freelancer to fix a PLEX IPTV issue I'm experiencing. Streaming IPTV works on some devices, but not others. ello I installed plex server and all runs fine, but i am having issues with my IPTV playback. phone, TV, PC wont play, But my firestick, Ipad will play the IPTV just fine.
Errors I'm getting:

TV error: "Playback error"
Iphone error: "Couldn't create the playback session for this item"
PC plex error "Error code: s1001 (Network)"

I am wondering if its a transcoding issues or router?
Thanks!