Solution using command line for Windows, Linux, and MacOS
If you have updated your GitHub password on the GitHub server, in the first attempt of the git fetch/pull/push
command it generates the authentication failed message.
Execute the same git fetch/pull/push
command a second time and it prompts for credentials (username and password). Enter the username and the new updated password of the GitHub server and login will be successful.
Even I had this problem, and I performed the above steps and done!!