Its the launcher, check standard troubleshooting for mods: (double check everything in the launcher first)

引用自 EssoBunny：

1. Clear cache
2. Resubscribe to rt56
3. Delete the mod_registry.json file and the mod file located in documents/Paradox Interactive/hoi4 (I personally don't use this method because whenever I tried to do it, it just broke all of my mods, but it might work for you)
4. Verify the integrity of your game files
5. Do a quick and normal reinstall of the game (As in just press uninstall and then reinstall)
6. If all else fails, a clean reinstall of the game will fix all of your problems 99% of the time. It's a pain in the butt to do if you're doing it for the first time since you have to uninstall all of your mods, but it really does fix everything. But before you do unsubscribe from all of your mods, make sure to either favorite all of them or compile them into a collection. (Here's a guide on how to do the clean reinstall: https://kaiserreich.fandom.com/wiki/How_to_do_a_Clean_Install)

thanks clean installing worked for me

Just tried everything suggested above, but somehow, even thought the mod appear in my playset, it never loads. Any suggestion that I can use, please help?