This is what the support guy from company told me, I figured it might help others too...
Thanks for the message, I can help you out. What's your bioload like in the tank? It's possible that the tank is "too" clean, and there's not much for the skimmer to pull out, especially if you have a very light bioload. Also, let me know if you're using any other forms of filtration, such as a refugium. Make sure that the water level isn't too low in the prefilter box. If the pump is sucking in air, these bubbles will displace water, reducing the amount of pressure delivered, which is important with this type of skimmer. Optimum water level in the prefilter pump chamber would be just below the "teeth", which is high enough to ensure that the pump isn't sucking in air and allows for some evaporation as well. I would also scrub out the injector by unplugging the pump, removing the white access screw on top of the injector elbow, and running the supplied brush down through the nozzle a few times, just in case something's stuck in there. There are times when the lowest setting will not necessarily give you the most skimmate - I find that raising the cup a bit often funnels the most bubbles into the collection cup. I like to set the cup so that the square base is right at the top of the bubbles (you may need a flashlight to see this). Try these things out, and let me know how things go. Hopefully we can get the skimmer to produce more skimmate, if possible. Thanks again!