Player Fitness / Stamina not replenishing

I bought osimhen for my team, and idk how it happened but after a game his fitness level just remained stuck. no matter what training plan i put him on his fitness is staying the same, not increasing. and it isnt a visual bug either because i tried playing a game with him on this fitness and he starts off fatigued and slow and his stamina goes down but never goes up. any way to fix this or does EA have to do something in the new update because now the career mode is basically ruined because my main striker is always going to be slow and tired.