I have been trying since January 2020 to install Sourcetree. I have contacted the community and the company several times and have tested all proposed solutions with no success.
The problem is that the installer hangs indefinitely after authenticating my account with the "Next" button disabled and only the Installation item checked in the column at the left.
I am attempting with v3.3.8. The most recent attempt was performed after updating the Internet Explorer 11 Internet Options to enable "Access data sources across domains".
I am able to install and use Sourcetree from a Windows 10 computer.