Try deleting your object thumbnail cache and see if that helps. Some cc needs a different program than CEP, it's named something else with some cc I got from some sites, and if I don't have their version of a CEP type program installed that cc will not show up, even if it is closer to the top of list. And I suspect the reason for that in my game is because they are conversions from other games like Far Cry, AC, Silent Hill etc.
ETA: It's a known fact some cc is not filterd into the right categories like you will find some wallpaper at the end of the thumbnails when looking in game, but they should be at the front etc. (their thumbnails). The TS2UC is a mess when it comes to how it sorts cc. We used to could depend on cc being at the front of a category, but not anymore, you may have to flip through several pages to see someting but when it was just EPs etc. separately any cc was always set by cost and any floors or wallpapers were always at front, but TS2UC doesn't organize these things that way anymore. I have noticed this many times. And it could also be the creator, too. There is an article somewhere over on MTS about this. However, it's also a known fact some cc and or especially mods may not work if they are in subfolders.