I've got the same problem, except debugging only worked once for me (after cleaning the project and enabling all three options in debug configuration).
I'm working on OSX too, so perhaps it's related to the platform.
Did find any further information on the problem?
In Preferences/Dynamic Languages/Debug setting Port to 'custom' and adding a static portnumber solved the issue for me.
Not sure if you're still having this issue however I struggled with the same problem. I eventually got it resolved. Have a look at the following post:
Hope this helps.