Couldn't you just Torrent Trackmania 2 and once downloaded sign in with your legit account?
I ended up having to do this as well, tried to download it from maniaplanet several times, only to give up and resort to downloading some cracked Russian version. About as much as I expect from Nadeo tbh.
I ended up doing the same thing eventually. Terrible customer service. Almost makes me wish I just pirated it in the first place.