Can't find TV show using "Fix match" with Agent=TheTVDB but I find it manually on thetvdb.com

If a few kilobits is 5% of your monthly allotment - time to find a new ISP, pay the overage or stop using Plex. <---- it can only go downhill from here.

Are you using MP4/M4V files?
If so: Move Local Media Assets to the bottom of the stack of active agents under ALL tabs for Shows and Movies:


Red: Where it was
Green: Where it goes

If you’re not using MP4/M4V files - name and structure your files correctly:
https://support.plex.tv/articles/categories/your-media/

If you are naming and structuring your files correctly then you might try clearing your TVDB cache:

That’s all the standard stuff that usually fixes problems like yours - Usually.