As more recently seen in “Permission failure cloning in Git in Windows”, try and launch GitHub Desktop after:
(warning: read comments first)
git config --global core.sshCommand "'C:\Windows\System32\OpenSSH\ssh.exe'"
That will ensure GitHub Desktop to use the right OpenSSH ssh.exe, instead of an internal one, as seen in desktop/desktop issue 5641.
If Git bash does not work properly after that, you can either:
-
revert the configuration:
git config --global --unset core.sshCommand -
or use the Git for Windows SSH
git config --global core.sshCommand "'C:\Program Files\Git\usr\bin\ssh.exe'"
If C:\Program Files\Git\usr\bin\ is already in your %PATH%, you don’t even need that configuration: the ssh.exe from Git For Windows would be the one selected by default.