Jay, no air.
Lets think about this for a minute.
With a couple of quarts of cheap hydraulic oil in the reservoir tank, that should be enough for a test run and flush, the pump should pick this up and send it to the steering controller. From there it gets returned to the reservoir tank, so no problem here for air, because after 5 minutes running the engine, the pump would have pushed any air back to the tank. Might need to rotate the steering wheel a couple of times.
Then the other side is the two lines to the steering cylinder from the steering controller. Perhaps loosening the fitting at the cylinder for each side to visually check for oil leaking out would indicate oil is getting that far. Two person job to watch for a squirt of oil when wheel is turned in that direction. Leaving fittings just barely loose will help prove it's under pressure.
Air in the cylinder itself. My experience with hydraulics is that the seals will leak out the air until the cylinder fills with oil. Seals are only oil tight not air tight. But this will also take a little time.
If all this doesn't work, you will need to have someone do a pump pressure check at the line feeding the steering controller. No pressure, bad pump. Then another pressure check at each line feeding the steering cylinder. No pressure, bad steering controller.
Process of elimination done in the correct order should show results.
Common mechanics technique.
Don't get frustrated, get methodical.
Good Luck.