can't receive chat messages from a certain number.

I'm not receiving chat messages from a particular number. 

I receive mms messages from the number in group texts, but no chat messages in our solo thread. Which is how I know the messages are being sent.

The number is not blocked and I have done the suggested trouble shooting .

Call in support has not solved the problem. I'm using a new phone and Sim and am still not receiving  chat messages.  So if I could get access to a ticket that  would be awesome.