I bought up game pass ultimate for a couple years onto my xbox account recently.

My 13yo son actually uses the xbox one s under his account but up until recently he has been able to access and download games while logged in on his account using the game pass. Now he can only download games under my account but can still play them on his account.

He is now trying to download add ons to games but if he downloads them under my account the dont come up on his account. If he tries to download under his account it says he needs game pass  or to buy but when he clicks on gamepass it comes up manage account but wont let him download. 

Under both my account and his account the xbox is set to home. 

His account is linked to mine under the main microsoft account. 

Any suggestions as googling seems to suggest everything should be working.