Let's start from step one.
Take the cup off. Adjust the bubbles so they just start to overflow out of the skimmer body. Reinstall the cup. Wait a day or two. That's it.
In the picture you posted the bubble level is WAY too high.
If it won't skim it's possible you just don't have enough bioload. Five fish in a 150 isn't much. I have the same skimmer (the SSS version) in a 70g setup, also with five fish, and it works great.
Take the cup off. Adjust the bubbles so they just start to overflow out of the skimmer body. Reinstall the cup. Wait a day or two. That's it.
In the picture you posted the bubble level is WAY too high.
If it won't skim it's possible you just don't have enough bioload. Five fish in a 150 isn't much. I have the same skimmer (the SSS version) in a 70g setup, also with five fish, and it works great.