This is a common problem that can have a few different causes. First, check to make sure that all of the cables between the monitor and the computer are secure and plugged in correctly. If that doesn’t fix the problem, there are a few other things you can try.
One possibility is that the monitor is not getting enough power. Make sure that the power cord is plugged into an outlet and that the monitor is turned on. If the monitor has a power button, make sure that it is lit up. If the monitor is still not getting power, try plugging the cord into a different outlet.
Another possibility is that the monitor is not set to the correct input. Most monitors have more than one input, so you might need to switch the input that the monitor is using. To do this, look for a button on the monitor that says ‘Input’ or ‘Source’. Pressing this button should cycle through the different inputs. If the monitor is still not displaying anything, try pressing and holding the button for a few seconds. This might reset the input to the default setting.
If you’ve tried all of these things and the monitor still isn’t working, it’s possible that the monitor is defective and needs to be replaced.