I had this problem after I had installed gpg through Homebrew first, and then uninstalled it to use MacGPG instead.
I solved it by going to Sourcetree > Preferences > Advanced, then for GPG Program I clicked Browse and selected /usr/local/MacGPG2/bin. After that, I was able to enable GPG signing on a repository.
I was able to make it work with Homebrew. You need to create a symlink gpg2 -> gpg under `/usr/local/bin` and after that you can select `/usr/local/bin` as GPG Program path under Sourcetree -> Preferences -> Advanced
Turns out I had installed GPG tools, it said it had a key in the control panel thingy so I figured it was cool beans... but it turns out I didn't have a private key yet. So I clicked new, entered a password, jigged my mouse and keyboard some and it all came good.
Hello Sourcetree users!!! With the recent removal of Bitbucket Cloud account passwords for app passwords (please see our Bitbucket Cloud community post for details on why we made this change for se...