Couple of things, i can think of. Sometime there is a key eg. To switch to an external display does this do any thing? The Graphics drivers - do they see the new display? Is the Cable HDMI at both end's? Does the Cable work if you plug it into a DVD player and the same TV?

1. Sharp Tv Monitor Driver

Sharp Tv Monitor Driver

Does the Laptop need to have a certain HDMI version to send the data to the TV? Are you running the resolution of the graphics card at a compatible resolution for the TV? Can you supply the Thread with the exact make and model of both the TV and the Laptop?