If you aren't already using Git 2.19 I'd suggest upgrading to that and switching Sourcetree to use it as a System Git in the Tools/Options/Tab.
There have been some issues with earlier release of the Git Credential Manager that handles credentials for Git for Windows.
Supported Platforms macOS Windows We recently introduced support for additional hosting services such as GitHub Enterprise, GitLab (Cloud, Community Edition, Enterprise Edition), and...
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