Check warnings.log (My Documents/My Games/Company of Heroes 2/warnings.log, open with notepad) for errors. Search for the title of your mod (Control+F) and see if you can find something like "invalid file structure". If that's the case, then you haven't followed the instructions correctly.
I did follow the instructions correctly. It turns out, the mod preview image I added was a 340KB JPEG of a helmet - the game would not load my mod with it.
Relic Entertainment
cblanco ★ 
보드카 중대 
VonManteuffel 
Heartless Jäger 
