This message is displayed if either the device you are using has been rooted OR has a custom ROM (custom version of Android) installed.
Some manufacturers install their own custom versions of Android which will generate this error message as LockLizard only support non-modified versions of Android. Many budget brand tablets have custom ROMs installed, whereas major manufacturers (like Samsung, LG, etc.) usually install non-modified versions of the Android OS.
If you have an Android device from a major manufacturer and want to check it is rooted see unrooting an Android device.
Note that clone devices (copied/fake versions of a device) are always rooted.
If your device is not rooted please email the device brand and Android OS version to LockLizard support so we can test this.