Sims 4 PS4, cannot host a toddlers birthday party?

@K8eP1 I have the same problem sometimes. Unfortunately I haven't found a way around it other than just letting the sim age naturally or aging them up without throwing a party. So here's the best way, I think: Turn aging on, then turn the lifespan to the lowest setting it will go, or not depending on how quickly you want your toddler to age up. Since your sims are vampires, they won't age (if they are young adults), except for your toddler. Eventually you will get a notification saying "It will be (your sim)'s birthday in a few days". Then when a day or so passes, you'll get another saying "It is (your sim)'s birthday today!" This is the day when you can throw them a party. After they've aged up, set the aging back to whatever you want. 

That's how I've been doing it. I hope it works for you!

Oh well, I'm not sure. I've never done that. You could always try resetting the sim properly by enabling cheats. But keep in mind that enabling them makes you unable to earn trophies on that save file.

I have this problem with my teen vampires - who were turned while teens and are now turning into young adults. The seasonal calendar says it's their birthday, the game tells me to throw a party, but the party planner says nobody is having a birthday. Can only assume the game can't tell the difference between vampires that are still aging up and the ones that can't. Either way, you can throw, and plan in advanced with seasons, every other type of party, but not a birthday. That said, nothing prevents us from throwing a normal house party and serving birthday cake. At least some of the guests will still gather around the birthday sim when they blow out candles no matter what the occasion is.

EDIT: forgot to say: I'm on PC and the vampires have been bugged to all hell since release.