Apple has released iOS 9.2.1 to the public. The update brings a fix for an issue found when devices with a mobile device management server, among other things. The update can be downloaded now, either over-the-air or through iTunes.
Here's what you'll find in iOS 9.2.1:
This update contains security updates and bug fixes including a fix for an issue that could prevent the completion of app installation when using an MDM server
for information on the security content of this update, please visit this website: https://support.apple.com/HT201222