GetDeviceId is returning blank in blueprints

I need to fetch the device id. Basically, I want the windows mac id to be more precise. The documentation for GetDeviceId mentions
“If you do not have permission to call this on one or more of your platforms, set GET_DEVICE_ID_UNAVAILABLE=1 in your build step to ensure that any calls that may be made to this API will simply return an empty string.”

I already did this in the .Build.cs
PublicDefinitions.Add(“GET_DEVICE_ID_UNAVAILABLE=0”);

Despite rebuilding the solution, this is not working. Please help!

Thanks in advance