Hmm... Strange...
I went to my game and aged my teen sim up, then I immediately went to click on the places where sims can apply to universities:
- Mailbox showed the option to apply
- Computer showed the option to apply
All that before the graduation ceremony too.
All these following should apply here:
- Sim must be a young adult, adult, or elder to apply.
- An exception to the first rule allows teens to apply too if they have graduated early.
- A sim who have been expelled or dropped out can still apply. They can only attend distinguished degrees and have the basic degrees locked out.
- Sims who have applied can apply again after some days. This is to give them another chance of getting into distinguished degrees.
I'd strike this as a bug now.
I'll ask additional questions here:
- Have you tried repairing your game?
- What trait did your sim get for graduation (it should appear when they age up)? You can check it from the sim's trait panel or pick another sim and open the young adult's Sim Info panel from the relationship panel.
For now, the only thing I can suggest is enabling testingcheats, shift-clicking on your sim, go to Pack Cheats.../Expansion Packs.../Discover University (wording may not be exact) and there's an option to enroll your sim.
