I am unable to send messages to a contact on my iPhone

i go to text this person and my texts aren’t saying delivered and he’s not getting them. but when he texts me i still get them but his texts that he sends me are green. i even try to call him and the call goes through and he can answer it and we can talk perfectly fine. and another thing is i can still see his location. but all my other texts are sending to everyone else. it’s just him that my texts aren’t sending to. i’ve tried restarting my phone and it didn’t work.

[Re-Titled by Moderator]