1. Create a new local repo with SourceTree.
2. Add code to it.
3. Commit.
4. Use Hg-Flow button to add Hg-Flow to this repo. Accept defaults.
5. Now press the Hg-Flow button again to perform an action. Notice that you get the Hg-Flow Initialization dialog again instead of the Hg-Flow Actions dialog.

This only happens with newly created repos for me. Previously created repos work fine when pressing the Hg-Flow button.

I find this with SourceTree 2.74 on my Mac Mini and 2.76 on my Macbook Pro.