If it worked when you bought it, but when it got home it did not, make sure you connected everything in the head correctly.
From the body up to the head you will have more than a couple cables. Verify the manual.
Make sure (with power off) that all cables are properly seated.
Then if all that does not work, disconnect all the connectors on the bottom of the CPU board and retry to see if the display come up. There should be a 10 sec delay before they do.