1. Check if the screen settings are accurate (e.g. if TV Input matches to the correct source).
2. Check if the HDMI/DP/VGA and Power cables are firmly or properly connected on both ends of the screen and device.
3. Reboot the TV/Screen to see if signal gets re-established.
4. Reboot the device to see if TV/Screen will look for input signal, it is possible that the EDID is not retained by the device. Otherwise try a different TV/Screen to test with device to help isolate and identify if issue is related to display or device.