@BlondieWarrior95 I'm having the same issue as you at the moment; there is nothing in my sim's calendar about Prom, they can't invite anyone to Prom as there is not even a High School section in the pie menu when clicking on the sim I want to ask, and at the time Prom is supposed to start I don't get the pop-up asking me if I want to travel there or skip it.
These teens (they're triplets) are only 1 sim week old and are on a long lifespan. They aged up on a Saturday and I did get the 'Do you want to go to prom? pop up that day, and I said yes but nothing happened, they didn't go. I followed them to High School on the Monday and a new Principal has been generated as Mei Prescott is dead in my game. I played for 3 days at the High School and hoped that, as others have said, going to High School and generating a new Prinicpal would enable Prom to work, but as explained above on their second Saturday evening as teens I couldn't do any High School/Prom interactions with any other teens from the Pie Menu and no pop-up appeared asking if I wanted to go. It will be interesting to see what happens on their 3rd Saturday as teens!
Incidentally, I am also currently playing a teen in a different save with aging off and she did have Prom in her calendar, was able to ask others if they wanted to go with her, and I was given the option to follow her to Prom when Saturday came around, so maybe this issue is also related to sims being on long lifespan?
