Why aren't I receiving texts from 1 other Galaxy S6 user?

[AC Question]

Not receiving texts from 1 other Galaxy S6 user

I have the Galaxy S6. Normally when I text my cousin who also has a Galaxy s6 my messages to him are green as to where there are orange when I send to a non s6 user. About a week ago They stopped being green and reverted to orange, and I can send him messages but I can not receive messages from him. I don't know any other s6 users to see if it is all s6's. I can receive messages from all other devices.
Thanks in advanced for all your help.

 

[Almeuit]

Re: Not receiving texts from 1 other Galaxy S6 user

Which app are you using to send texts?

 

[MrOutdoorsman35]

Re: Not receiving texts from 1 other Galaxy S6 user

I am using the stock messaging app