Backhoe Attachment on NH TN70D

[Parksman]

I have a New Holland TN70D with three valves on the back. Two operate the front end loader and a third valve operates the grapple. I bought a used backhoe attachment and tried hooking it into the valve that the grapple uses but can't get it to operate the backhoe attachment. I tied the valve open and can see the hydraulic lines to the backhoe move when I activate the valve from inside the tractor but can't get it to operate the backhoe valve. I tested the backhoe on a smaller and older John Deer tractor than my New Holland but it only had one rear valve which I'm assuming was just a pass through valve without any remote controls to it since we didn't do anything except plug in the backhoe lines and start operating it.

The backhoe is a Bobcat 765 which is a smaller unit and my hydraulic flow should be move than enough to operate it.

Does anyone have any suggestions?

Thanks for your help.