Sync Up Error When Inviting Contacts

We purchased a new Sync Up watch for our 8 year old, and sadly 4 days later, we STILL can't use it.  When we send invites to contacts that we've added, they get different errors.  Three or four different errors reported from friends and family.  

TMobile has NO idea what to do…  they opened an engineering ticket and called earlier (4 days into this) and just said they are still "working on it".  Meanwhile, our boy is sad as he was so excited for his new tool for independence!

Anyone have any idea how to fix this?  We are beyond frustrated.

¡Gracias!