You could try a zero grind from center to edge with no relief.
You would need to take the guide off the grinder.
Old Gerber daggers were hard to get really sharp.
Steel was selected for blade toughness not ease of sharpening or edge making/holding abilities.

are the belts worn out?

I sharpened 10-12 knives, the kitchen knives were pretty bad, did the Gerber on that belt, switched to another new medium grit and still no edge on it,  nice and shiny though. Went back to the first belt, and did a couple more pocket knives, which put a quick edge on them with 4-6 pulls.  It's some tough steel. More grit? Higher RPM's?

 

I sharpen knives on a different type belt sander but same principal.

Usually when I am having trouble getting a knife sharp its because I am not using a coarse enough belt.

The result is that the edge is not getting ground down and it is still dull and rounded.

Get a sharpie and blacken the edge on both sides.

Make a few passes on each side and see if you are grinding all the way and removing all the marking.

Once you get all the way to the edge you should have a wire edge or burr for the full length of the blade.

Then start stepping down to finer belts.

Go slow and don't get it too hot.

With the work sharp and the correct belts you should be able to put a nice edge on just about any knife.

Im not sure how much you know about sharpening.

One idea to understand is you are sharpening at the lowest grit.
You are refinining/polishing as your grit gets finer.

If the knife isn't getting sharp you may need to use a more course grit.

I like to use a starting grit that puts an edge on the knife quickly, then move on honing the edge.

Drop down to a lower grit, give it a few swipes to see how the blade reacts.

Another problem you might be having is you could be reprofiling the edge and just haven't reached the apex yet because the grit you're using is too fine to do it quickly enough.

I personally wouldn't want to keep any of my good knives on too long, and would rather use a course grit for shorter 'bursts' than a finer grit for a longer duration.

I went to the coursest grit and then back down and finally got an edge on the Gerber, not nearly as sharp as the one I put on my Kershaw launch, which now shaves hair off my arm. I never truly understood about the differences in steel, I'm going to work on the Gerber some more. Are the leather belts any use for stroping? Or is this just hype?

 

I don't have one of these.
Are you asking if you should buy a leather belt for stropping, or did it come with one and you're asking if stropping is hype and worth your time to do it?

Stropping is not hype.
It can knock off burrs and align the edge after sharpening.
Some steels like VG-10 I find require stropping to get good results.

You should definitely strop.
Use light pressure (lighter than you think)

Thanks- have one on the way-

 

OP, I got this from Amazon a few months ago. They fit the Ken Onion WS (but not the regular WS)
http://www.amazon.com/x12-Leather-Honing-Polishing-Belt/dp/B017WR81WM
I've only used it a few times on my Busse Team Gemini, it worked well and is made in USA.
ETA: It's a 3/4x12" leather honing belt for KO, in case the link doesn't work.

The extra fine belt is 6,000 grit and serves as the stropping belt. No real need for a leather belt IMO.  There's also an ultra-fine belt that's 12,000 grit.  The leather belt just affords you the ability to load your own polishing compound.

If you can't get the blade shaving sharp with the extra-fine or ultra-fine belts then it's something in your technique with that blade and buying a leather belt isn't going to fix the issue.

Gerber used some very hard stainless for their blades.  I had a Bolt Action that was hell to sharpen, but would hold an edge for a long time.  You might need to just work more with the coarse belt to re-shape the edge.  I also have that sharpener and sometimes it seems like forever to get a blase edge re-shaped from previous sharpenings, especially if the effective bevel is being changed.