I can’t verify child account so he can play online

Plants Vs Zombies is advertised as pegi 7 and online maybe aimed more at age 10 plus but my son had been playing online for a long time however he can't play online at all anymore the verification aspect dosent go through, yet if I go onto my adult account on his switch it lets me using my EA account? This is unfair if you pay for the game for your child they should be able to use online features! Hes frustrated because he won't be able to use his saved progress from his online account.