Interesting. I recently tried to throw a birthday party for my vampire twins (aging from teen to YA, they were born vampires) and got that "no one is having a birthday" message and threw a dance party instead.
I just ran into this again, with two teen vampire twins aging up to YA (again). The party was scheduled for 7pm but it was 6pm when I was trying to schedule the party.
My only option for birthday Sim was a vampire child whose birthday it is NOT (she has a week left). I was also doing the Master Chef Aspiration for their great-aunt so I made it an ungoaled dinner party and then spent the party cussing out poor Simeon Silversweater, the unruly guest who snubbed our gourmet dishes in favor of getting leftover wedding cake, stole a piece of cake between age-ups (thereby forcing us to bake a second cake), and generally made a nuisance of himself. Dude, I get that you’re stomping around angry, and I guess you thought binging sweets would help, but I’m not inviting you again even though I love you. (He’s the dad of another Sim in this save and an NPC roommate in said other Sim’s home.)
Vampire Mom used command to order him to clean in revenge. He cleaned out the fridge, then got a THIRD piece of cake, ignoring so the dirty dishes everywhere, so… cleaning up the cake. Worst. Party guest. Ever. 🤣
(Ironically, his NPC roommate quirk is… throwing constant parties.)
