Although I don't actively chase the mastery stuff, I usually check my stats when the game opens out of idle curiosity. I note that everything seems to have reset to zero over the past couple of days. Anyone else have this? On Xbox BTW.
I saw all zeroes on PS4 too, but logged out and logged back in and it was all back. Maybe just a glitch with the year change. Numbers on the Stats page are all still there too.
Mastery used to open every time I started TSW but it just stopped weeks ago. That didn't bother me as I'm not interested in it, the enjoyment of driving trains is reward enough for me. I had a look at the stats page out of curiousity and the last activity it registered was in November, when the class 31 came out. As far as I can tell, I'm logged in, because I haven't logged out but I can't see anywhere an option to either log in or out.
I just logged into the website and checked all my Mastery done to this point and all is still there and it has not been reset and that is on PC.
I just tried looking at it from in the game and it appears right now not available to access it, hopefully it will come back up soon.