I get the following message in windows command prompt:
D:\Github\UnrealEngine>git fetch upstream fatal: unable to access 'https://github.com/EpicGames/UnrealEngine.git/': SSL certificate problem: self signed certificate in certificate chain
This was working previously. Not sure if this is a local or server issue.
Try updating your git maybe. Github recently changed things about the authentication.
It appears my Anti-Virus program is interfering with git. I had to pause protection and start a new console window to get it to work. I also updated my git for windows. It is working now.