Need help - no motion using prismatic joint with pulley system

I have a simple telescoping tube model, where the linear motion is controlled by a pulley system. The drive pulley is powered using a hydraulic motor and gearbox. I can get this to work if I use a cartesian joint to define the telescoping tube DOF. I set very small limits for the two axes that shouldn't have motion. The issue with this is when I use it in my larger model, I believe it is causign kinematic constraint issues.

When I attempt to switch the cartesian joint with a prismatic joint, I no longer get telescoping tube motion. I confirmed that the prismatic joint is setup correctly by commenting out the pulley system, and using an external force to move the telescoping tube. So there is some issue with how I've defined the prismatic joint with the pulley system. Attached are three versions of the model, as described above.

Can someone help point out what I'm doing wrong? Thanks in advance.