Interesting. I wonder if Norton set up a Firewall rule to block updates?
I had forgotten all about Windows Update settings on the Modern/Metro side. I pinned a tile for the Desktop version on my Start Screen and was using that, although not very often for I have it set to auto download and install. I do go there after Patch Tuesday to make sure all is well. I see there's no way to pin the Modern/Metro side WU setting to the Start Screen. Best I can do is type "update" in Search which brings it up.
Anywho, glad you got your problem fixed!