why do I not receive alerts when an iMessage has been sent to me

Perhaps you have notifications turned off for messages, or you have "do not disturb" turned on.

I have this same problem with an iPhone 6.

I have tried disabling and enabling iMessage and notifications for iMessage, but do not get any notifications for incoming messages. This means that there is no sound, no vibration, no banner, no alert, and nothing in the notification center.

The only indication of a new message is the app badge.

I Have this problem with my iPhone 6+ and my iPad Air 2. You at least get a banner, I get nothing...I have tried every suggestion from the Apple Community and others as well; but nothing has helped. Mute, do not disturb are both off. The tone is set in sounds and the volume is high. At this point I guess all I can do is give up and just periodically check my iMessages throughout the day. I'll keep checking back to see if there's a suggestion that wasn't here before.

I will admit; I'm more than a little bummed out about this. And to make it even worse, I don't get alerts on my Apple Watch either. It seems that none of my Apple products are working as they should. 😠😠

I started having this problem today. Not getting any notification on my phone (5s) of an incoming message. The only way I knew I had a new message was the tap on my Apple Watch. I have checked all settings on the phone and I should get an alert, but nothing. Only thing different is updating to IOS 9. 😟