If you are at an actual Starport (4x8 facility on a planet with a lot of bright blue coloring) it should be powered and spawning cp ships should work.
One caveat: if you docked your current ship inside the Starport docking bay, you must exit your ship (so you are standing in the docking bay) to use CP ship market.
The ships you spawn will be created in the most north westerly grid outside the Starport grounds but still adjacent to it.
If at landing pad it must be powered and you must enter it on foot as well (not be parked there in your ship). If there is a flashing (blue?) at the landing pad it is NOT powered, but if no flashing light it should be powered.
I buy a lot of CP ships. DM if you like with questions.