Same issue here after upgrading from 2.2.0 to 3.0.0, I can't get the System Console to load. I get the SC menu, but the main window only shows "Loading...", and clicking anything in the menu doesn't give any response:
My setup has an nginx SSL proxy in front, and I can see these two lines appearing in access.log when i try to access the System Console:
"GET /api/v3/admin/config HTTP/1.1" 500 0 "-" "Mozilla/5.0 (Windows NT 6.3; WOW64; rv:46.0) Gecko/20100101 Firefox/46.0"
"GET /api/v3/teams/all HTTP/1.1" 200 952 "-" "Mozilla/5.0 (Windows NT 6.3; WOW64; rv:46.0) Gecko/20100101 Firefox/46.0"
I'm also pretty sure config.json was touched after the upgrade, but unfortunately I forgot to copy it before rolling back to 2.2.0.