From the Leviton web site: 7599 > Duplex > GFCI Receptacles > GFCI Ground Fault Devices > All Leviton Products from Leviton Electrical and Electronic Products
The indicator light could mean that it's wired incorrectly. Try swapping the line-load wires? Even if the circuit was wired by a pro, it would be far from the first time an electrician got his wires crossedA line-load reversal diagnostic feature is provided which prevents the GFCI from being reset and stops power from being fed to the GFCI receptacle face or through to downstream devices. A green LED indicator on the GFCI's face also illuminates to alert the installer to the line-load wiring reversal.
Also it could just mean the receptacle is bad. It's not too common that this is the case but with electronics, I have learned to be suspicious of anything fresh off the assembly line.