Sliding door driver's side 2000 Sienna non-power door will not open. What shall I do?

I have not owned the non-sliding door model but there may be an interlock connected with the fuel door (since the sliding door would hit the fuel door). Try opening and closing the fuel door and then see if the sliding door opens.

Hi, John! Thanks for getting back to me. The problem has been fixed -- but don't ask me how. I was at a doctor's appointment for one hour and when I came back, my friend who was waiting for me said, "Your door is fixed." I asked several times what he did to fix it and he just kept saying, "Nothing." Wish I could get an answer in case someone else has the same problem -- but no luck. In any case, thanks for your reply.

You should test out the fuel door idea, just so you know. With the sliding door shut pull the fuel door release lever and then try opening the door. You'll know right away if that was the trick your friend figured out and you can fix it yourself next time :)