Regarding the recent issues: Either there's a bug in the recent Plex Transcoder or Plex have stopped supporting .m3u8 streams.
Most if not all IPTV providers support MPEG-TS (.ts) streams - please use these for the time being! I am working on a version of telly to automatically transcode .m3u8 to .ts.
Thanks to @EnorMOZ for looking into these issues with me!
If you run into any issues please hop into our Discord or open an issue!