Check your cable, is it too long? Try switching it out first just to make sure its not a problem with the cable itself. This has happened many times to me, so its always one of the first things I check:
Also (WINDOWS KEY + P) command, will bring your project menu. And try selecting "duplicate" and see if that pops it on.
Also: once you have determined that it is not a problem with the cable, and the above WINDOWS+P command doesn't work, go to your desktop>right click anywhere on desktop>display settings> how many monitors are listed there after you click "identify" then "detect"?
After trying the above....if it still nothing....Id disconnect the monitor's hdmi/display cable, update your GPU drivers, then reconnect the HDMI/display...