Zero Turns

I just purchased a zero turn mower model number RZ5424/... at my local Sears Outlet store. It was a return with only 1.7 hours and appeared to be in great shape and you would expect with that little usage. When I got it home, I started it up and everything seemed to be fine. However, in trying to aquaint myself with its operation, I found that it would only turn in a counter clockwise circle. It seems to me that only the right lever is engaging the the right tire. When I hold the right lever in neutral and move the left lever forward, nothing happens. I tried moving the tracking adjustment in both directions but still I had no movement on the left side. The Sears store has said that they will send a service person to my house, but they are booked for the next 10 days. Any thoughts on what could be wrong? Is there anything that I should be checking on my own?

Thanks