imessage working for some contacts and not for others
I've just set up an iPhone 6 as a new phone for my daughter (handed down from a big sister). It is for messaging between her and parents/sister when she is at home, so no SIM card and being used over WiFi only - this was the same as the previous setup for the older sister before she graduated to a SIM card. The phone has been completely wiped and set up as a new phone.
We are having trouble getting iMessage to work properly - I can get it to work between her and myself, but it won't send messages between her and her mother or her and her sister. Interestingly, this did appear to be working last night after initial setup!!! Now, every message says 'not delivered' and when trying to send a message to her mum's or sister's account, it comes up with a green message rather than a blue one.
I have tried:
- logging in and out of iMessage and iCloud, with variations of rebooting phone in between or not
- the phone is updated to latest iOS (12.4.4 on that iPhone is the latest I can get)
- deleting threads and also deleting contacts and re-adding them
We are tearing our hair out trying to figure what could possibly be causing this and it appears nothing that we are trying makes any difference.
Grateful for any ideas that can be offered.
cheers
iPhone 6