2004 Kubota kx91-3

Hi. I have a Kubota kx91-3. I added a thumb to it. It is plumbed up to the thumb area and has a pedal for it. My problem is that the thumb will only move in one direction. I found that the valve will only pull and will not push to reverse the flow of hydraulics. Any ideas on how I would go about making it work both ways? Thanks