Any version of LetMobile. Specifically when you are re-enrolling a device into LetMobile.
During the enrollment process you get an error "Device exists" or "Device is already enrolled".
Login to the LetMobile User Portal and make sure that your device has been removed from the LetMobile Server. Once logged into the User Portal click on "My Devices" to see if your device shows up, if it does you will need to remove it prior to re-enrollment.