Group Texts Message Stopped Working Yesterday

Yesterday afternoon, I was able to receive and send group messages, but in the evening I got an error message when trying to reply to a group text message and haven't been able to send them again. I receive them, but can't send them. I have tried multiple group message conversations and tried starting new ones. I get an error with an exclamation mark. I have a Galaxy S9 and have never had this issue before. Please help. 

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