What is the most likely cause of display problems on a monitor that is not working?

The most likely cause of display problems on a monitor that is not working is a faulty power or video cable. This is because the connection between the monitor and the power source or the computer itself is crucial for the display to function correctly. If either of these cables is damaged, loose, or not functioning properly, the monitor will not receive the necessary signals or power to display an image.

In this context, while an outdated operating system could potentially lead to issues over time, it is not the immediate cause of a monitor failing to display anything. Insufficient storage space likewise affects system performance and operation but does not directly impact the monitor's ability to present images. Damage to the motherboard may cause a variety of failure symptoms, but again, it is less likely to be the specific cause of a monitor failing to work compared to a direct issue with the power or video cables.