Comment by jmuhlich

Also if the upper tray is height-adjustable, check the rubber one-way valve flaps in the middle of the supply tube that runs up the inside rear wall of the basin. If any of those flaps are damaged or missing, water will leak out there instead of being directed to the spray arm depending on which height position you're using. If you're lucky, you might still have one usable height position without replacing anything. Otherwise you need a whole new supply tube ($60-100) as the rubber part doesn't seem to be sold separately.