Group text messages suddenly not working
I am on a group text with my sibling. Dad is sick, need to be in touch. Did not receive message from one person in group text, but we were able to send and receive individual texts. iPhone 6s, iOS 11.2.5. Did not update to 11.3 due to others having battery problems. Rebooted twice. I am still in the grlip and have been added again. Also turned on iMessage for a time, but shut it off. Turned on Cellular, but no change. Turned it off. WiFi is working well. 12GB of 16GB used.