How you can tie yourself up in knots......
I could not login to the App Store from my hack, no matter what I did. I changed everything, serial numbers, IDs, logged out of everything, you name it, I tried it. I went on the internet checking out and trying URL after URL post, and nothing. I could login with my Apple ID, even to Music, but the App Store was always no. I was now into the troubleshoot several hours and zippo.....no progress and nothing worked.
I was desperate, and was just about to post here.....but then I remembered something.
I remembered to use ifconfig to check my network interfaces....and I found no en0. I had an en2, etc, but no en0....
uh-oh....
I sort of remembered from a long time ago that this could be a problem, but couldn't remember what Apple process it would interfere with.
So, why no en0? Because I'm a bit over the top about not enabling excess stuff in the BIOS that I don't need. I had disabled the ethernet interfaces in the BIOS because I was using my Thunderbolt 10G adapter.
So, then after hours and hours of unnecessary troubleshooting, I re-enabled them, even put a driver in my config.plist, but did not plug in an ethernet cable to either of the built-in ethernet ports, and bingo, even without an ethernet cable plugged into it, en0 was there!
But, would it allow me to login to the App Store? Yes!
You know I really have to curtail my "sense of economy" in the future....
Thought this might be useful to show that even those of us who've been around for a while can overlook some obvious issues when something is not working.....