Causes of Second-Monitor Problems
Secondary-display problems usually come down to a few basic causes:
The computer can’t support the display in color depth, pixel count, or interface options.The monitor’s cable is damaged or malfunctioning.The computer’s display drivers aren’t handling the secondary display properly.
How to Fix Second-Monitor Problems on Windows and macOS
Follow the steps below to diagnose and fix the cause of these malfunctions. In macOS, navigate to System Preferences > Displays. Select Default for display, or press Scaled and choose the correct resolution. In macOS, navigate to System Preferences > Displays, and adjust the Refresh Rate drop-down menu. USB-C and Thunderbolt monitors are even more confusing because the cables are physically interchangeable but not cross-compatible. DVI, meanwhile, has multiple versions, and it’s possible to plug an incompatible DVI cable into a computer or monitor.
