This Mac posted solution just worked for us: macOS Sierra: Open an app from an unidentified developer.
Specifially, we followed these instructions:
- Note: You can also grant an exception for a blocked app by clicking the “Open Anyway” button in the General pane of Security & Privacy preferences. This button is available for about an hour after you try to open the app.
To open this pane, choose Apple menu > System Preferences, click Security & Privacy, then click General.
Good luck!