Why has Joe not answered my request to view and purchase his 2007 Volvo C70 ?

It's been a month and the ad is still running and the site will not permit sending another request to see the car and I'm still waiting. My hope was that the site mgr. would alert the seller that a buyer is trying to get an appointment to see the car.

Joe went to the bar and never came back. Somehow I think that after a month of no answers the car is probably sold.

You are missing the point. If the seller is not responding, why is it not the responsibility of the website manager to contact Joe and resolve the issue or delete the ad?

Seriously? There are hundreds of thousands of ads, no one could police every single seller. Anyone else would have given up after the first day or so. I give you high marks for persistence and perseverance for pursuing a lost cause.