Who I have the same questioned this topic

I have 2 child phones on my account and pay for Verizon Smart Family Premium.  One phone, no problems.  The other phone the invite text is not being sent to the phone.  I have tried manually installing the companion app on the other phone but when I do it gives a message saying the phone is not active for Smart Family.  All 3 phones (mine and my childrens') are Samsung Galaxy S21 5G with the latest software updates installed