This happened to me in beta (I think I bugged it but not sure) and again yesterday. Was wondering if it was a bug and if it has happened to anyone else.
So, the first time through it I rescue Marta and it prompts you to beam out and sends you back to Sector space. Once there I see a prompt in the system access pop up that says to continue Roadblock. I also notice that the mission isn't completed and there is not prompt to hail Starfleet. So, I click continue and it starts me in the instance again. After completing it a second time it works and can hail Starfleet to finish the mission.