If you have a Surface Pro 8 connected to a dock station, disconnect it and try to connect the monitor directly to the computer to confirm the problem is not the dock.Disconnect all peripherals (such as printers, cameras, and USB devices) to confirm none of the other devices are conflicting with the display.Connect another known working monitor to determine that the issue is not the graphics card.Connect the monitor to another computer to see whether the problem is with the external display.Change ports if the monitor and graphics card feature multiple ports.DisplayPort and HDMI come in different versions, so check the manufacturer for requirement details to ensure you have the correct cable.Change the signal cable to confirm you are not dealing with a bad cable.Disconnect the signal cable from both ends, wait 60 seconds, and firmly reconnect it.Check the signal cable connection between the monitor and the graphics card.

Use the monitor's built-in controls and select the correct input port.Turn the computer off and on to refresh the connection.Confirm the monitor is connected to a power source.

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