Most likely the PC is set to a higher video resolution than the TV can handle.
If you set the PC to the native resolution of the TV it should work.
You may also have to change the order you boot the PC and select the input on the TV that it's connected. It might take 5-10 seconds for the PC and TV to "handshake" so give it some time. You can also try changing the input and then back to the PC.