OK, so if that tractor has position control, which I believe, that means you need to adjust the rod/stop that cuts off the hydraulics when in the "up" position.
But first, I'd run it without the backhoe on to make sure the backhoe wasn't interfering with the 3-pt getting to the up position. If it does, use a knob or stopper on the 3-pt lever to prevent you from trying to raise the 3-pt all the way up when the backhoe is on.
Some tractors will have a flip-down lockout to prevent the 3-pt from being raised above a certain point when a backhoe is attached.
If this tractor doesn't have position control, then check the 3-pt lever linkages to make sure it's not sticking in the up position, and again make sure the backhoe isn't blocking travel.