FYSA:
I run a IPS/IDS and application based firewall (Untangle) in front of my Windows 10. The moment I put my desktop computer in bypass mode on the firewall I received an instant connection to the game.
I assume with this knowledge you can likely do the same with IPTABLES, UFW, or pfSense to see if it works. Pop a hole in the firewall to prevent any form of NATing that replaces your header after it scans your outbound traffic.
Hope this helps a few of you all… I gotta head to work or I would expand upon this and see what is causing the issue.