Q: IOS 9.2.1

Check your settings in Messages. See if there is a problem with your iMessage being activated.

I have the same issues since the device was updated 9.2.1.  iMessage activation fails, and trying to use the Apple ID for iMessage simply hangs when trying to authenticate.  iMessages is completely bricked and unable to be fixed.  Guess it's time to take a trip to the Apple Store

There is a little bit of troubleshooting that you can do for iMessage activation. One of the biggest is to ensure that you are using a supported carrier. If so, if you have turned off iMessage, understand that they expect you to wait 24 hours. If you turn it off again after turning it back on, then the 24 hours starts over again. Make sure you have a text messaging account with your carrier, as activation requires a hidden international SMS to be sent to the Apple servers in the UK. I did not have any difficulty with mine. I updated a 6s and an original iPad Mini. Both activated just fine. Actually, I even decided to restore my iPad to factory, and after entering my Apple ID, it activated right away. You may want to try to do a reset on your device. Hold the sleep/wake and home buttons together until you see the Apple logo and then release. The device should reboot, and it will not affect your content. Another thing you may try is to go to Settings>General>Reset>Reset Network Settings. That may clear any issues there are with connections.  If you get an error when trying to activate iMessage or FaceTime - Apple Support

Ah I figured it out.  The date & time setting wasn't set to 'Set Automatically'.  I enabled that and reactivated iMessage without an issue.  Guessing between the iOS update and the setting not being 'Set Automatically' it causes iMessage authentication issues because it's not matching up the correct time with the server.

I'd suggest that the original poster see if their 'Date & Time' is also not 'Set Automatically'.  Thanks.

I am have an issue with my sms/iMessage alerts. I have my volume up and it's not on silent. I'm just not getting the message sound alert, anyone else???

This has nothing to do with the subject of this thread. If you want to try and get some help, it would help if you started your own thread in this same forum, however with a subject line that defines what you are experiencing. Then phrase your question to describe your problem, and then explain what troubleshooting you have tried to correct the issue. Your question will be buried in this thread, since it is about something else.

Having  similar issue. Won't send or receive. We have toggled off/on iMessage. Powered off/on. Reset. Checked date and time. Still nothing. Works for a bit but then stops. suggestions please 

Not only iMessage. Can't pick up this phone. All functions in setting became very slow or dead. Screen freeze but still can get other app's message except Apple's basic functions.