Cannot get propane to flow

Today, I opened the spitter screw as you suggested. The tank on the right which is the one we have been using had only gas escape. The one on the left had liquid coming out. I didn't leave it open long enough to completely drain the liquid but I can do that tomorrow. But I am thinking since I had the selector on the regulator pointing to the tank that was not completely full I should not have had a problem. I am also wondering if I should open the 3 burner knobs on the stove before I turn on the propane tank valve. I will also weigh the cylinders tomorrow and check the label for tank weight.