Member Tools Texting - Lists not working

On or around Dec 9th, about the time my iPhone updated, the send a text message to a list function stopped. I tried making the lists smaller (around 6) and it still will not send them. I have been using this function for months and have loved it. Any ideas what happened. This has been such a valuable feature.

Do you have group messaging enabled under iOS Settings > Messages?

Have you tried restarting your device? Maybe it will fail with the sim card, you should also remove it and reinsert it.