I submitted a bug report in game but if anyone had this problem and might know a solution.
So i just did the world quest lighting the flame challenge (quest name might be wrong) in maldraxxus.
When completed my weapon transmog reverted to its original look and i couldn’t mog it back. Its on my walrock where i have a dagger and off hand mogged to legion artifact staff.
I went back to loot the great vault and got an upgrade and i still can’t transmog anything.
I tried using the mount and visited different transmog npc’s.
Also tried relog and restart the game but nothing helps.
Maybe it’s just temporary but still worth to mention here as im curious if anyone else had this issue.
Edit: Mogging armor parts alone seems to work but not weapon.