The word lamp aways means a bulb. What you and I call a fixture, or sometimes even call "lamp" is in trade lingo called a luminaire.
There are many possible hookups for fluorescent lamps and luminaires, especially in commercial buildings. I would not try to comment on your problem without seeing the wiring diagram on the ballast and the wiring diagram for the luminaires.
If your ballast is made by Advance, they have such diagrams on their website.