iMessages not being received

I recently got my first iPhone (6s) after having Android phones for the last 8 years. My son also has an iPhone (5s). When I send him a text, he does not receive it. I have tried sending messages with imessaging turned on and also with it turned off and he still does not get my texts. This never was a problem when I had an Android and he had an iPhone. I suspect it has something to do with switching platforms.

Any suggestions how to remedy? He receives my phone calls OK, so, I suspect I have not been blocked.

via iLounge Forums http://ift.tt/2cuqar4