Hi UkAudi, hope all is well!
I'd like to ask, how inclined are you toward purchasing a different skimmer vs continuing to invest more time towards this one? Unfortunately, this skimmer is typically associated with a bad reputation (SeaClown

) and you will receiving many great recommendations towards a different model, but let's be sure that's a path you're looking to follow or if you're still wanting to make this puppy work.
If the former and you're looking for something different, tell us about your tank, your water volume, your bio load, and your other methods of filtration you currently have.
If the latter, then let's start with some troubleshooting. 6 months is plenty of time to run and have it broken in. During this time, did you have it hanging over the back of your aquarium or have it in separate sump? How often did the water level fluctuation in your display tank or your sump?
Here's a tip I found that may help. Have you tried this?
"Open the air bleed until you see a bubble in the intake tube then close the air bleed just until the bubble goes away. Try this a few times to get a feel for the right setting on the air bleed. I know that the Seaclone does not have a good rep, but my experience is that it works just fine, consistently producing a dark concentrated skimmate. You do have to keep the foam filter clean.
A tip on using the Seaclone, or other skimmers, is that using Amquel or other water treatments/stress reducer will stop your skimmer from properly foaming. It can take a week or more for that stuff to work its way out of the tank."