That's what happened for me
Mine used to change every time I leveled up in my career and suddenly it stopped changing them period. I talked to someone from EA and they said my game might have a bug, but they didn't tell me how to fix it.
If you're using cc, try removing that. Otherwise, try repairing the game through Origin
I'm not sure what cc is, and I don't know how to repair it through origin. They were the ones who told me I might have a bug and sent me to some Forum.
CC = Custom content you download from third party sites
Repairing: Right click on the game in Origin and hit repair game
I have the same problem in the Doctor career. A post I found said you were supposed to get a new uniform at levels 2, 4 and 7. After 2, however, the uniform remains the same - green scrubs - even though I get a message that my promotion comes with a new uniform. I had a bit of CC installed, so I removed it, but the uniform remained the same. I then started a new game, with a new sim, and cc disabled. This time his uniform never changed from the original blue scrubs as he was promoted.
