there's a hex screw adjustment on top that regulates the depth that the blade will reach. it's not in any of the manuals as of yet, although in the past i have mentioned to see if rick can put it in the supplemental manual update. this issue has come up before on here as several others have indicated that they received similar out of the box. i don't have time to search right now but perhaps you can find the thread or have others point you to it so you can see photos of the thing i'm talking about. if you're still having no luck, i'll try to take a picture of mine when i get back.
first thing though, set your trenching lever adjustment to deepest it will go and bring the blade down without starting it and look from the side to make sure it was not that before you adjust the other thing.