It looks like you haven't gotten a response to your post yet. If you could answer the following questions, it may help others in the Apple Support Communities get you to a solution:
Please describe what you see next to the message: Is there an alert or error? Is there an icon of some kind?
Is the message received by the person you've sent it to?
What is the current iOS version number listed under Settings > General > About > Version (example, iOS 11.2.6)?