mesh collider problems

Hello everybody!

I was trying to do a moviment with a plataform, I have exported a project from maya, and then I set the mesh collider with him. I make a simple script to make his moviment, but it seems not work.

The script can be found here http://pastebin.com/u32qLXs7, the tag "elevatorGround" is the tag that i've created and set on the plataform. Every time that I stay in the plataform, the bool variable does not change and the elevator does not move :(. Does anybody know what issue is that? And how I can fix it?

Thanks :D