Stuck: The Centre Cannot Hold

bwbriscoe

I'm attempting to complete the 'Besieged' chapter of 'The Centre Cannot Hold'. So far I've completed:
-Answer hail from Enterprise
-Assist Allied Vessels
-Defeat Hostile Fleets
-Answer Hail From Enterprise
But I'm stuck completing:
-Restore Control to Starfleet Vessels

I've restored control to two, but I can't find the third. There's the green ring but no ship in sight...help!

Thanks, Ben