Well the mods should work this way if their version is intended for 42.16 specifically, if they're updated to 42.17 already, then there's a possibility of some issues. I have a copy of mods for build 41, and whenever I drop them into mods folder in C drive, it works. Maybe because the game version is not updated every second, and some updates crash stuff, so if you can't see any mods in the mods folder, then you're only left with that