Ran a clean install of vanilla from Mojang, ran launcher and created a world. Then closed MC and ran forge-1.14.3-27.0.60-installer.jar, got this error:
Debug log shows this:
I'm having the same issue. Fresh install of vanilla, opened launcher and started a world. Closed MC, and ran 1.14.3-27.0.60 installer, most recent, and am getting this each time.
Edit 1: Debug.log shows this: