can't host party

I'm having the same issue. It says I need to host a birthday party before any other parties can unlock, and I need a new trait in order to have a party. I switched one of my traits hoping that would be sufficient but it still didn't help. I have all four active slots filled and I don't want to retire any of my sims. Does that mean I can't ever host a party?

@JCGooch18 You need a Sim that has got a new trait in order to unlock the first party. Unfortunately you need to retire a sim and create or promote another before you can select a new trait. 

@SalixCat is it possible to have a baby, grow it to adulthood and make it an active player in order to achieve this? and then switch one of my current sims back into the active/playable spot? i dont want to retire/lose the ones i currently have, but would be ok 'deactivating' one of them for a while.

@JCGooch18 

Sorry, it's not possible to reverse retirement but it's possible to change the new playable Sim's appearance so he or she will look similar to the Sim you retire. 

I can't really host party's because I have too many sims in my house the host party is available but guests can't attend because it tells them the party's already full. Not sure how to correct that other then move out all the inactives and retire some.

@EloquentSickness 

There is a maximum limit number of players that can attend a party. I can't remember the exact number. 

This message will pop up to any player that tries to join a party that is already full as there is no room for several guests. 

There is nothing wrong with your parties or your household. You don't need to get rid of any of your Sims as they don't count as guests. They are the hosts 🥳 

Was this an open party or closed?

If you want to give your friends a better chance to join your parties before they are full, I suggest that next time you try hosting a closed party. In this way only players in your friends list will be able to attend.