@snazzymay Ok. Then probably not what I was thinking.
Just because a file shows in the cc list at startup doesn't mean all that much. That just lists the files that have extensions that the game recognizes. But it won't necessarily load them if they are broken or the wrong format for the game. TS3 also uses packages files and TS4 won't read them for example. I doubt all the files you show in the pic are broken or the wrong format though since it's so many and they appear to come from different download sites.
I know you said you think you're running the 64 bit game version but the other big reason that files won't load usually is that the game is the Legacy edition. To check that, you need to run a dxdiag and look to see for sure which version of the game you are running. It'll tell in one of the first couple of lines. If you see 32 bit Windows listed, then you're running Legacy. If that is the case, then newer CC may not work with that version and would explain what is happening.
One thing you can try is to delete the localthumbcache file. It's a good thing to do when you add or delete CC from your mods folder. It contains all the thumbnails you see in CAS and elsewhere in the game. Deleting it will make the game regenerate all the thumbnails. It's safe to do and the game will generate a new one the next time you start. All you'll notice is it takes a second or two to regenerate the thumbnails in CAS, build and live modes.
And if that doesn't work, you can try a repair.
If none of that works, come back and we can go from there.
Hope this helps.