iMessage without SIM card no longer working
A friend has been away on a month trip, so we decided we would communicate via. iMessage. We assumed that she could continue to use iMessage when she was connected to wi-fi networks without the need of her SIM card. We tested removing the SIM before she left to ensure she could still receive iMessages on wi-fi only and they did, but now, messages I send out are going out as text messages rather than iMessages.
Why does iMessage no longer work?