Bicha pokemona

You are right about that but gen 7 starters cannot be caught in the wild as of yet (which means they can't be in any ball but regular pokeballs) and I've checked the event database and all Primarina line events were given out in regular pokeballs, so I believe the ball is the issue here.

I just tested and shiny Lunala, Solgaleo and Necrozma can now be used in online raids! Mine were made with pkhex but they are legal.