The next thing to consider is if you’ve chosen an angle that is acute enough to give you the results you’re seeking. If you have chosen a very wide angle, your knife will not be as sharp as it would with a more narrow angle.
The last thing to look at is the newness of your sharpener because your new diamond plates are not yet broken in. Your diamond plates require a number of sharpenings to knock off the loose diamonds before they start to really give you great results. You’ll find that the more you use them, the better your edges will get. New, out of the box, your diamond plates will produce fairly rough, ragged edges which won’t be very sharp when cutting paper or shaving hair; they’ll be great on tomatoes though. As your stones break in, your edges will get more and more refined. Edge refinement is important because it influences how your knife will cut in a given application. Every abrasive, like your diamond plates, makes scratches on the bevel of the knife. Ideally, those scratches extend all the way to the edge of the blade where they form micro-serrations. A very coarse stone will create deep, wide scratches that will form large, jagged teeth at the edge of the blade. A fine stone will create very small teeth. Depending on what you’re cutting and how you’re cutting, you may want bigger or smaller teeth. The general rule of thumb is that more aggressive teeth are best for cutting soft or slippery materials, especially when cutting with a slicing or drawing motion. Good examples of where a toothy edge excels are cutting rope, tomatoes or zip ties. Extremely small teeth and a very polished edge are great for push cutting applications like shaving, chopping and carving.
Here are some images contrasting the edge of a knife that’s been sharpened with old, well worn 600 grit diamond plates:
and another that’s been sharpened with fairly new 600 grit diamond plates: