Sourcetree's registration depends on a WPF Web Control that in turn relies on Internet Explorer and it's settings.
If you can log directly into https://id.atlassian.com via Internet Explorer then registration in Sourcetree should work.
If you have any issues logging in via Internet Explorer our best advice as of today for registration webview issues with IE is as follows::
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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