My situation is I have Github username that joined my company Organization on Github.
Whenever I log in as that username on SourceTree, it can't detect any repositories.
I recognize that SourceTree only looks for personal repositories on my account, not the repositories on my company that I'm in.
The only option I have manually cloned the repositories and then add them to SourceTree. It's painful and takes time.
Thanks for reaching out! Is your company's account an Enterprise account? If so, have you tried connecting your Github organization to Sourcetree? You can follow the steps at Get started with Sourcetree. Remember to choose the Github Enterprise option.
If you still can not see your company's repositories that you have access to, please let us know which Sourcetree version are you using and which OS so we can continue helping you.