Please confirm you're looking under Local and not Roaming AppData folders.
(which contains accounts.json)
Otherwise, check if you're using System Git (%ProgramFiles%\Git) rather than Embedded Git (%localappdata%\Atlassian\SourceTree\git_local\mingw32\bin).
Refer to this KB article:
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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