FC25 on X-box not recognising Game Pass

Hi - Newbie Boomer Dad helping frustrated son, and hoping for some answers to bring peace to the Den......We have purchased FC25 Ultimate and have Game Pass on an X-box S that is working fine (and has been for 1yr+) other than FC 25 won't recognise the subcription is active, and so won't allow multiplayer / Rush etc. We have only one X-box/MS account (mine), on my profile, with only one console set to Home Console and my son's X-box profile on the same X-box with the same X-box set as Home Console. Yet FC 25 requests we sign-up to Game Pass - this is on my son's profile/EA account combo, or mine with my own EA account..... The forums suggest 'log-out, restart' 'restart modem' 'contact X-box' etc as the cure, but I'm reasonably tech savvy enough (hah! we will see!) and have been through all those steps as well. BTW we don't have/haven't used the EA App - is there something there I should look at? Thanks!