MC Command Center is practically required to bypass some of the crazy bugs that are out there these days. You maybe able to remedy with a console command or a mod to change the relationships status. Cursory google search did say something about promised teens unable to propose. It's possible that promised or engaged sims maybe broken functionally and you will have to do the first thing I mentioned. but cannot do anything outside of those things until they're young adults. Teens I believe can 'fool around' and 'promise to be engaged'. If you're not modded then do the first thing I mentioned because it's likely some kind of bug. Young adults, however, should be able to do all of those things. Teens can't woohoo, ask for marriage or sleep in the same bed. like the 1-3 years of teen numbers (17-19) you can be and not be in high school. This game has too broad of a scope for age brackets.

I know you've said young adults here, but I feel like you're talking about teens.

It would likely give you the option to 'quit' the high school or university 'job' to allow you to do another job. You could also assign them a job temporarily, maybe that would fix it. something like 'Sims 4 commands to graduate university' should pull up the appropriate commands or MC Command Center mod maybe able to help cheat them out of university promotions or what have you. You maybe able to find a console command cheat that will have them graduate university, you'd have to look that up.

Things you can do to move them forward is age them up with a cake or via CAS commands in full edit mode. They should quit on the birthday of Young Adult. If they're going to high school and you are not modded, then that is a bug. If you don't want them to do that, then have them quit university.

Young Adults can go to university if you have that installed. or if there is no topic start one.This site covers only the use of the modding program sims 4 studio.ġ. go into it and check the 'me too' and add in what you see to the topic. like 'YA still going to high school' and if there are topics with that up. You want add in the search what you're seeing. First things first, if you're not using mods and you're seeing odd behaviors like these, take them to EA answers headquarters.

Sims 4 teen and adult relationship mod