Sims 3 athletic skill not improving?

I have had The Sims 3 for my laptop for about 6 years and everything has run smoothly. I have a few mods, mostly just outfits and hair. I have a vampire and a fairy and they recently had triplets. The male vampire cannot improve his athletic skill to level 3 no matter how much I work him and I've tried bringing him to an athletic class, resetting the sim, and have had him try working out at the gym, at home, on the television, stereo, etc. Basically I followed all advice already online. He still will not gain skill which is very frustrating because I'm trying to make him an astronaut. The skill for the fairy will go up but not for him. Please help!