The Full Lock does not work if there are other profiles installed on your device, if you have an outdated Flipd profile installed, or without an internet connection. If you're having trouble, please delete all profiles you have under device management (including Flipd) by going into your iOS Settings > General > Device Management > Delete. 

Then, reinstall the Flipd profile, swipe Flipd closed from running and wait 2 minutes. This will give your device some time to recognize the profile. Once you have re-installed the profile, and have ensured your phone has an internet connection, you can enjoy using the Full Lock.