Using the viewsonic remote control, press the Input or Source button and check whether you are on the correct input. If the correct input is selected and there’s still no signal, check the source where the signal is coming from. Some models have both HDMI 2.0 and HDMI 1.4 Inputs. Plugging an HDMI 2.0 signal to an HDMI 1.4 port may cause a blank screen and vice-versa. If using a Windows-based notebook, press the Windows Key + R and make sure the Project settings is either on Duplicate or Extend. A defective HDMI or VGA cable can also cause a no signal problem.

https://www.viewsonic.com/viewboard-faq/display