Q: Cannot send group texts/messages or voice texts.

This doesn't really help me as much; I know how to send texts, and I am able to do so to individuals.  It's just that I can't get group texts to go through.  I have service and am sending to both iPhone users and non-iPhone users.  Interestingly enough, a moment ago a particularly long text I tried to send to an individual non-iPhone user was not delivered.  Does anyone know if there is some lingering issue with messaging on the iPhone 6 Plus?  I have the latest iOS software update.