I cannot send or receive group messages. My last phone couldn't do this, and my upgrade that came in today (Iphone 5s) cannot either. However, other devices in my plan are able to. Group/ imessaging is enabled. I can group message with people whose names are in blue when I type them in, but if I add anyone with a grey name it does not let me send messages. I also cannot be added to a group message with contacts that are in grey as well. The people that are grey in my contacts are able to be in group messages with others.
Any help? Thanks!
Group messages travel over the data network... I'm curious, were you connected to Wi-Fi at the time? Resetting the network settings disconnects the Wi-Fi connection, that's why I'm asking.