TVDB -
The TVDB is user editable… we (the internet at large) would all appreciate it if you’d create a corresponding entry in the TVDB 
This is often as easy as referencing the IMDB entry, taking only seconds to save many others the same frustration…
(If you wonder why Plex (or any of dozens of other apps) don’t just use IMDB for metadata, it’s $$$. While TVDB allows API calls (this is how metadata requests are handled behind the scenes) for free, this is apparently not the case for IMDB, who require paid agreements in the tens of thousands of dollars for similar API access… annual Plex Pass for $999 anyone?)
File / Folder Naming - I’ll echo the responses of others concerning proper file naming. In OP’s case, simply naming the ripped file properly in the first place would have averted this problem.
Manual Match -
I’ve ended up in a similar situation after using third party apps to rename my files, and manual match is how I fixed it. It’s a bit cumbersome for large numbers of files, but great for one offs that aren’t matched automatically. YMMV
