Hello edee64,
Welcome to Apple Support Communities and thank you for posting your question here.
Let’s see if we can work together and find out what’s causing this behavior. You’ve already done some really good troubleshooting on your own already.
Have you seen and tried all the steps found in If you can’t send or receive messages on your iPhone, iPad, or iPod touch?
Is the person sending the messages on Apple or Android? We just like to know which one we are working with.
Do you have another Apple device? If so, do you receive the messages there?
Is your iPhone updated to iOS 14.3 (if compatible)? If needed see Update iPhone, iPad, and iPod touch.
Reach back out and let us know more details.
Take care!