Can't send iMessage to one person
I have an iPhone X and my sister has an iPhone 6.
Both up to date with iOS
Both have iMessage activated.
We both receive and send iMessages from and to friends but not to each other.
We both rebooted our devices numerous times, turned iMessage off and on again. Signed out and signed back in from our apple IDs a couple of times.
We both have access to Wifi and network data.
We both still have green arrows when sending messages.
iMessage does not work only with each other...
Please help 😟