On family premium but family member cannot join

[rainboiboi]

Hi,

Can someone contact me regarding this? I sent an invite link to my brother and gave him the screenshot of the address i entered (to make sure it is in the correct format), he signed up and it was working until few days back when it all suddenly stopped. 

When i tried to send him another invite, it says address entered is wrong. I'm sure i didnt change the address (how do i even do that?) so please help me out. 

Thanks,

Derek