why are my text message not blue anymore?

I think mine maybe green because I downloaded Cortana because after I downloaded iOS 11 my iPhone 7 just restarts in the middle of typing messages taking photos or whatever.... got a lot worse. So, that is why I put Cortana on my iPhone so when it happens if I’m not on my Mac i can text from my windows computer (had to buy one for a computer programming class).

If your text messages are green then they are being sent as SMS text messages, when they are blue they are being sent via Apple's iMessage service.

They can only be blue when you are sending message to other iOS users who have turned on iMessage on thier device.

Do you still have iMessage turned on? Check in Settings > Messages

what is waiting for activation?

Do you have Wifi or 3G access at the moment?

It will be trying to connect to the Apple servers to activate iMessage.

If you do have internet access then try resetting your iPhone.

Press and hold the Home button and the Wake / Sleep button at the same time, keep them pressed until the Apple Logo appears.

II'm having the same problem ... Apparently it's a glitch in the apple software you can do a full reset or wait a few weeks for apple to issue a patch.

I had the same issue...I tried a reboot and it worked. No more issue. All iMessages are now blue.

--To reboot, hold down the Home and Sleep button until you see the Apple logo.

Hope this helps.

iOS 7.0.2

Wassup