Re: New CAS mods not showing up anymore
One thing you can try is to delete the localthumbcache.package file. Doing that forces the game to create new thumbnails in CAS and the build/buy catalog. It is safe to do and the only effect you will see in game is that it might take a couple of extra seconds for the thumbnails to regenerate in both CAS and the catalog, the relationship panel and any type of selection panel like for cooking, baking, etc.
It is good practice to delete the file whenever you change your CC and mods before starting your game, especially if you remove a lot of things or are constantly moving CC in and out of your mods folder over time. The thumbnails of the items removed will still be there in the file when they aren't needed anymore. And it seems that, deleting the file also fixes other things that crop up like being unable to select more than one other household sim to travel with the sim initiating the travel. So, you might notice a few little things like that as you play as well.
Hope this helps.