I can’t send group messages

Go to Settings>Messages>Make sure that MMS Messaging and Group Messaging is turned on. If it is, then contact your carrier to tell them to check your account to make sure that you have SMS/MMS active on your account. If they say yes, tell them you cannot send a group SMS/MMS. That is their feature and they have to troubleshoot it.

If your service provider is VERIZON, log into your My Verizon account, search for "Blocking". Choose "Block calls and messages on my mobile device". Choose your phone. Under "Block Services > Messaging" see if "Block Picture and Video Messaging" is active. If it is try turning it off. This will let SMS messages through.

Worked for me!