I have the same problem. For 10-14 days I have tried to upload my (first) app without any luck.
Today I uninstalled/installed xcode to get the latest Application Loader (version 3.6), but it did not help.
I can't validate the archive or upload it to app store. And upload from Application Loader does not work either. It hangs.
A few times I got an error message indicating that I can't contact Apple, maybe because TCP port 443 is being blocked.
But in macOS the firewall is off, and as far I can see my router does not block any ports.
I am running macOS Sierra (10.12.1), Xcode 8.0 (8A218a), Application Loader Version 3.6 (1020).
Did you solve the issue ?:
UPDATE:
Yesterday I made a hotspot with my smartphone, connected my iMac and retried upload with Application Loader.
And miraculously it worked...
God knows why - and why I did not try that before...
Best wishes, stigekalder