Cannot verify my app after “Xcode: process launch failed: Security”

Question

I have been working on an app for a couple of weeks but suddenly it does not run on the device any longer. Xcode returns:

Could not launch "MDInbox"

process launch failed: Security

and I get the "Untrusted Developer" pop-up if I want to run the app manually.

By "suddenly" I mean that I dont know of any upgrade I have done. It just stopped working after a couple of successful builds/runs on the device today. If I go to the "Settings"-->"General"-->"Profiles" I can do the following:

Problem is, that the app is still "Not Verified" upon pressing "Verify" on the last screen. The pop-up closes and the navbar is flashing for a millisecond .(btw. should it say "enterprise developer" if I am on a free developer tier?)

I have followed all the proposed answers in the following threads but nothing worked

• Xcode: Process launch failed - Security
• Xcode process launch failed: Security

To summarize all the action I have tried:

• Restarted both the device and my computer
• Deleted the ALL provision profiles on the devices & under ~/Library/MobileDevice/Provisioning Profiles
• Created a new Apple ID
• Installed Xcode 7.2 beta
• Started new projects from scratch

I use

• Xcode 7.1.1
• iPhone 6 (iOS 9.1)
• React Native
• Free Tier Developer Program

Answer 1

I have found a solution (workaround?): Upgrading to iOS9.2 Beta 4 + xCode 7.2 beta did the fix problem. I suggest that restoring the iPhone with 9.1 would also work.