If your cover is not sliding easily after installation and you have checked your roller cartridge spacing then you will want to check your rail seal. If the outboard portion of your rail seal is sitting higher than your rail (see photo below) then this can cause the gutter of your center panel to run on that seal. Having the gutter ride on the seal will make sliding your cover difficult.
Your side rail seal should be almost flat with your rail as shown in the photo below. If it is not, you can remove your rail from the truck and push down on the side rail seal so that it is flat with the rail. Make sure you push down on the seal the full length of the rail.