The same thing happened to me - funnily enough it worked the first time with my brother, but not the second time with my wife. Exact same procedure, all iphones. Weird. All accounts are now in their 20s in terms of levels, so plenty of time for it all to go through. Didn’t feel important enough to go through the pain of a support ticket.
Shame now that they extended the invite rewards, but I still don’t consider 100 gems and a few days of VIP worth the trouble arguing and providing evidence to customer support.