A second screen that has gone black, says No signal, or simply never wakes up is usually a five-minute fix. The order below matters: the causes we see most often are at the top, and each step rules something out.
Try this first
- Check the cable at both ends. Unplug the video cable from the monitor and from the computer or dock, then push each end firmly back in. HDMI and DisplayPort plugs work their way loose over time, particularly on a monitor arm that gets moved. If the cable runs through a dock, check the dock end too.
- Try a different port, and if you can, a different cable. Ports do fail. If your computer has two video sockets, move the cable to the other one. A borrowed cable from a colleague's desk is a fast way to rule out a cable that has been bent behind a desk for three years.
- Check which input the monitor is on. This one catches everyone. A monitor with several sockets has to be told which one to look at. Use the small buttons or the little joystick on the underside or back edge of the monitor, find Input or Source, and step through the options until the picture appears. If the monitor says No signal but the menu still comes up when you press the buttons, the monitor is fine and this is very likely the answer.
- Set the projection mode in Windows. Hold the Windows key and press P. A menu appears on the right with four choices: PC screen only, Duplicate, Extend, Second screen only. Choose Extend for two screens working as one large desktop. If someone used a projector recently, Windows may have been left on PC screen only.
- Restart with everything plugged in. Click Start, the power icon, then Restart, leaving the monitor connected and switched on. Windows checks for displays as it starts, so a screen plugged in afterwards is sometimes missed.
- Ask Windows to look again. Right-click on an empty part of the desktop, choose Display settings, scroll down and click Detect. You should see numbered boxes for each screen, which you can drag so they match how the monitors sit on your desk.
If you use a docking station
Docks are the most common cause of this problem in an office, because everything runs through one small box.
Unplug the dock from mains power, count to twenty, and plug it back in. Then unplug and reconnect the single cable that runs from the dock to the laptop. Many docks stop passing a picture after a laptop has been unplugged and reconnected a few times, and a full power cycle clears it.
Be aware that a laptop with the lid closed on a dock behaves differently. With the lid shut, Windows treats the external monitors as your only screens, and Windows + P options that mention the PC screen will appear to do nothing useful. If you are troubleshooting, open the lid first, get both screens working, and close it again afterwards.
Also check how many screens the dock supports. Some smaller docks only drive one external monitor properly, and a second one plugged in will stay dark no matter what you do.
If that didn't fix it
The next likely cause is the display driver, which is the software that lets Windows talk to the graphics hardware. Click Start, type Windows Update, open it, install anything waiting and restart. That covers most driver problems safely. Reinstalling graphics drivers by hand is worth leaving to us.
When you log the ticket, tell us:
- The make and model of the monitor and whether it says No signal or shows nothing at all.
- Whether it is plugged straight into the computer or through a dock.
- The cable type: HDMI, DisplayPort, USB-C, or an older VGA or DVI.
- Whether it has ever worked on this computer, and what changed if it has.
- Whether a different monitor works on the same cable and port.
Still stuck?
Log a ticket at portal.yougrowit.com.au or email support@yougrowit.com.au. If it is stopping you working right now, call 03 9028 4358.
Support hours are Monday to Friday, 8:30am to 5:30pm Melbourne time, excluding Victorian public holidays.
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