Git error fatal: Authentication failed

Go to the Control Panel and then navigate to Credential manager. Change the username and password from Git repository.

Usually, when you are pushing the repository, there is a pop-up that asks you to login to your Azure account.

You can also set the username and email in the beginning by setting the global variable.

These links will help:

https://docs.microsoft.com/en-us/azure/devops/repos/git/share-your-code-in-git-vs-2017?view=azure-devops

https://docs.microsoft.com/en-us/azure/devops/repos/git/pushing?view=azure-devops tabs=visual-studio