Not being able to verify apps I have an iPhone SE, running iOS 12. As part of a programming course I do, we made some apps. 4 in total. 

Whenever I try to open one of these apps I get this message:



However when I go to settings and verify it tries to verify it as shown here:



But then it goes back to say not verified. How can I fix this?

EDIT: I am connected to WIFI and it works
You have apps installed as "enterprise apps" - i.e. it is not apps installed via the App Store, via TestFlight or directly from Xcode as a developer. Enterprise app installation is supposed to be used only by enterprises installing their own custom apps on their own devices - it is not intended for public distribution.

In order to verify these apps, you'll need to have a working internet connection, and especially you must have unhindered access to https://ppq.apple.com Apple Support

However, it is not enough to have a working internet connection. The enterprise distribution account with Apple that was used to sign these apps must still be valid (i.e. subscription paid) - and the enterprise must not have revoked these specific apps.