Why isn't the monkey king allowed to attend the party with the other deities in American born Chinese

You've got all the heavy-hitters in Chinese mythology: gods, goddesses, demons, spirits. The Monkey King, who's down below on his mountaintop, hears the music off to the heavens to attend the party, which he assumes he's been invited to but the bouncer/guard isn't having it since the Monkey King doesn't have an