I've been playing this mission for over three hours now and still get stuck!
Still love it though.
I've planted my four spatial mines and ordered two air strikes. I've diverted power and the force field has dropped but I'm now supposed to get an Access Chip from a Romulan Officer.
The white circle on the map (and the virtual guide path) takes me to a roof top where six Romulans paste eight bells out of me everytime! They don't seem to want to die as their health doesn't drop much with any hits I make and then they recover.
The first tiem I got this far I had a support team I called but in subsequent respawns they are no longer available.