I have an iPhone 6s Plus, my mom is using an iphone 5 as an ipod. She only uses it at home when connected to wifi. So we usually imessage back and forth, me from my phone number, her from her apple ID (Email address). I send and receive imessages from all my contacts perfectly except her. She sends and receives imessages to others as well without issues. It had been working until 2 days ago. All the sudden when I imessage her it turns green and then errors because obviously she can't sent texts (only imessages through wifi). Same for her with me, it turns green and errors out. Any suggestions?