All sarcasm aside:
You do need to be at the cap, have earned all skill points AND spent them all. 0 left.
I ran into this one myself back around the start of the year, with the mandatory respecs because of the skill changes. Couldn't understand why slipstream wasn't unlocking on one of my admirals on whom I'd decided to punt (at least for the day) on where to put those last 500 points.