This error message is not from Covenant Eyes. It's from Apple's device controls, Screen Time.
Set Content Restrictions for Apps to 17+ in the iPhone® Settings app to fix the "Restrictions Enabled. Certain apps, features, or services can't be seen or used when Restrictions are on. To use this app, turn Restrictions off" error message.
Apple’s device controls are called Screen Time. A specific setting in Screen Time, Content Restrictions, lets you set an app age limit for the App Store®.
Apps above the age range cannot be installed, opened, or used. Apple rates the Covenant Eyes app at 17+, so you must set Apps to 17+.
Set Content Restrictions for Apps to 17+
- Open the Settings app on your iPhone®/iPad®.
- Tap “Screen Time.”
- Tap “Content & Privacy Restrictions."
- Tap “Content Restrictions.”
- Scroll down and tap “Apps.”
- Apple rates the Covenant Eyes app at age 17. So you must tap “17+” for Covenant Eyes to run on the iPhone® or iPad®.
- Return to your home screen, and you should see the Covenant Eyes app icon on your device.