Is that a plaintext file that could be repurposed for my app? I'm having the same issue.

Are you saying they enroll their test devices on your MDM which is already set up with the app configuration keystrings?

I'm trying to push the app to them via MDM after enrolling as that's how my MDM will install the managed config for the app. However, it seems the app wont install on their devices as it seems to need some extra certification ("cannot verify integrity"). Did you have that issue?