Problem sending imessages

[Mysticalmuse1]

My dad can send an imessage to my ipad with his iphone 6s but I can’t send one back. I used to be able to do it when he had an iphone 6. Is this a software problem related to the iphone 6 and 6 s?

 

[Just_Me_D]

On your iPhone 6s, go to Settings → Messages → Send & Receive, and then make sure that there's a checkers next to your Apple ID. If not, tap on your Apple ID to put a checkmark next to it.

 

[Ledsteplin]

Do as stated above on your iPad.