I was just experiencing this myself, so I know how frustrating it is. Like you, I tried a number of the solutions folks have suggested, but wasn’t having much luck. What seemed to work for me, was to run a fresh install with my anti virus and firewall (Bit Defender) disabled. I then ran the launcher as admin, while my anti virus and firewall were still off and it worked.
As I say, I tried everything else, but this seemed to do the trick. I didn’t fancy a source-code workaround myself
(Also, may sound odd, but make sure your iTunes is up to date, as well)
Same issue here (with BD). Disabled both BD firewall and windows 8.1 firewall, but still nothing changing. Already tried a fresh install and the TLS stuff in the Internet properties. Even made sure iTunes was updated (though I think that’s irrelevant). Been doing all of this by running stuff as admin. Haven’t been able to replicate TheStarsMyDestination’s success.
(for BitDefender useres)
→ click on Firwall-Settings (top-right corner at FireWall)
(don’t know the following exact translations, but something like)
→ “application rules”
→ “add rule”
→ “programm path”: find your “epicgameslauncher.exe”
→ network type (depends on your windows network settings, look it up or select all)
→ “Authorization” (wrong translation, I guess): Accept/Tolerate/Allow/Whatever
Maybe customize to your system, like IP-Version or whatever.