Have yo also double checked that the blower motor is getting power? You may have to unplug it and check the wiring harness with a meter. If it is not getting power, the problem is up stream (switch or dash control, etc)-- if the connector is getting power, then it may be time to pull the motor out and check it directly. When you say the motor won't come on I assume you mean you don't hear it, or feel any air coming from the vents. I wonder if something is restricting the fan cage from spinning (rodent nest or something equally crazy)--
I would start with a meter and check to see if you are getting electrictiy to the plug.