In iOS 9.2 Apple updated how Enterprise distribution works. The updated steps are below:
1) Install the Enterprise App. At this point the app cannot be run until you change a setting. Note: You must do this step or the menu in step 2 will not appear.
2) Go into the Settings app and select in General, then select Device Management
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3) Go into the Menu with the name of the enterprise developer and select “Trust”. Note: This menu will not appear unless you have tried to unsuccessfully launch the app. The step in step #1.
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That is it. Now that you have selected “Trust” you can now run the app on your phone.