Hey @z0rlac!
First of all welcome to the forum and congrats on your first post! I hope it is the first of many more to come.
Since TruckersMP does not support mods, no mods will show up in the mod launcher when launched from TMP. ProMods will only be enabled if you join a ProMods enabled server as well however it also will not show up in the mod launcher. If this is the case, ProMods should still work when you join a ProMods enabled server. Please let us know if this is the case.
Hope this helps!
Farm Shark