I can't receive invitations to shared photostream

Hello,

My friend started a shared photostream group and while everyone else can get the invitation every time he attempts to send me one it says

'Invitation cannot be sent to this phone number' or something of that manner

I've already made sure that Photostream and shared photostream options were turned on for my iphone and I am currently updated

It's driving us nuts trying to figure out what is wrong and I've been looking online for answer but nobody seems to have this issue