If you see the below message then it's because you already have an existing MDM on the device you are trying to activate. You can only have 1 MDM on a device at any one time.
The MDM can be ours or it could be from another parental control you may have tested, or possibly from your childs school.
HOW TO FIX THIS:
If you already have curbi:
1. Tap OK to close the error message
2. Navigate from the device to: Settings > General >Profiles & Device Management
3. Delete the "curbi configuration" profile
4. Then restart the device
5. Download "curbi kids" app from the App Store
6. Follow the prompts to complete the activation process.
If the MDM is not curbi's then you can't install curbi kids until you remove it.
If your not sure, send a screen shot in to support, and I can help you identify who's MDM it is.