If the Melco security dongle is not recognized, start by re-installing the Melco software. (if you run Windows 10, make sure you have Windows 10 Compatible Melco software). The next step is to update to the latest Sentinel Security Driver.
In Device Manager, you might observe the security dongle incorrectly listed under Other Devices as "USB Ultrapro." Installing the latest Sentinel Security Driver should allow the dongle to be properly listed under Universal Serial Bus controllers as "SafeNet USB SuproPro/UltraPro."