How to trust app on IPhone 11 iOS 14.5.1

Tap Settings > General > Profiles or Profiles & Device Management. Under the "Enterprise App" heading, you see a profile for the developer. Tap the name of the developer profile under the Enterprise App heading to establish trust for this developer. Then you see a prompt to confirm your choice.

Install custom enterprise apps on iOS - Apple Support

1. Is this your corporate iPhone? Then please contact the system administrator of your corporate
2. If it is your personal device, in that case, do you have any profile installed by your corporate/organisation/enterprise/School Management?
   1. Erase the profile added by you If you have installed a profile on your own --> Install or remove configuration profiles on iPhone - Apple ...
   2. Or please contact the system administrator of the organisation who provided the profile to you