There is a cam at the upper handle. Maybe the cable is hooked in the wrong end?

I believe the self propel cable should be connected to the cam that rotates upwards when you push down on the self propel bar.

I think that device is called a 'bell crank', having an axle in the center with a spring or cable-attaching hole on each end. It reverses the direction of motion. You have the attachments reversed. I no longer have a 'PP' mower to look at and see, but that's it IIRC.