I downloaded three different versions for windows, but none of them start, first they ask me for registration, I select bitbucket logo, it sends me to the page that says:
SourceTree has been successfully authenticated. You may now close this page.
And that's it, the installer does not do anything else and just shows me the same panel:
welcome to Atlassian Community.
For Sourcetree there is a log file which could help in debugging this case further by seasoned Sourcetree users.
Please kindly check if in the log file mentioned on this page an error is logged.
If yes the Community might be able to debug further - feel free to report back if you find an error in the log file.