App Store Error: "An unexpected error occurred while signing in. Your device or computer could not be verified. Contact support for assistance."

I've got a Gigabyte Z170X-UD5 TH motherboard and an nVidia GeForce GTX 1060 GPU on a Sierra install. I am able to log into the iTunes store and download music from my library. But if I try to download any of my purchases in the App Store using the same AppleID I get the error message in the post title. Anyone have any ideas? This is the last thing keeping me from hackintosh "success".

Also, even though the NVidia driver seems to be functioning I am unable to change the resolution of the screen from the control panel. Also sound doesn't seem to be working and I'm not sure how to go about fixing that.

Thanks in advance for your help.