Can't go to university family is "traveling"

A little while back my sim Shing got an oppertunity to travel away for two days. I accepted it but never took the travel.

Now I'm trying to send his kids, who just became young adults, to university. BUT I get a message saying they can't enroll, cause the adults are traveling... by all my sims are home on the lot. 

I've tried resetting the sims in question who are alllegedly traveling, I've tried moving them out... but I still get the same message... What can I do? I really want these sims to go to university.

Hope someone can help me.