1. Firstly check your connections are 100% OK
a. Check HDMI cable or VGA cable (Video/Display cables) is plugged into the board properly
b. IF you have a faceplate in your room your computer plugs into on the wall, check this connection too (looks something like shown below)
c. Check the display cable is plugged into your laptop/PC properly, check for any pulling on the cable or any movement from your port, if the cable has been pulling on the port for a while this could break it.
2. Check Display Output on board
Find what connection your board is displaying to, if your display cable is plugged into HDMI 1 and the board is set to display on HDMI 2, you will not see anything. make sure these are the same.
For a TV this will be under Source
3. Check windows display output
Press the Windows key on your keyboard +P (Win+P) which will open the Project select menu
Make sure Duplicate is selected if you want it to mirror your laptop screen
If none of these fix your problem please submit a ticket and a technician will be able to help on their next visit to site