Why doesn’t my laptop show up on the projector?

If you are sure everything is connected correctly, and you have turned on the laptop only after everything else is connected and turned on, you may need to use a keyboard command to tell the laptop something is connected to its external output port. Below is a fairly comprehensive list of keyboard commands as provided by the manufacturers, compiled by Extron Electronics and edited by United Visual:

http://unitedvisual.com/2tips/2tvp111.asp