External monitor not detected or “no signal”
Work through the causes in order, from the monitor’s input menu to USB-C Alt Mode and graphics drivers. Each step cites Microsoft or dock-maker documentation.
Updated: 2026-10-18
Run the no-signal check in the solver →
Fix it in this order
1. Monitor power and input
Make sure the monitor is turned on and its input source is set to the port you are connecting to [MS5]. A monitor left on its DisplayPort input shows “no signal” when the cable is in HDMI.
2. Windows projection mode
Press Windows logo key + P and make sure Extend is selected. If “PC screen only” is active, Windows does not send anything to the external monitor [MS1].
3. Take out everything in between
Microsoft’s first hardware step is to disconnect accessories: “Connected docks, dongles, adapters and other hardware can cause conflicts.” Test the simplest direct cable from computer to monitor first [MS1].
4. Swap the cable
Try a different cable. If the new one works, the old cable was faulty [MS1]. For USB-C, use the cable that came with the dock or monitor, or a full-featured USB-C cable: charge-only and data-only cables carry no video [PL3].
5. Try another video port, and another computer
If the computer has more than one video output (HDMI, DisplayPort, USB-C), try another one. Testing the monitor on a different system shows whether the monitor or the computer is the problem [MS1].
6. It worked before
Press Windows logo key + Ctrl + Shift + B to reset the graphics driver, then restart. If the problem began after an update, roll back the display driver in Device Manager [MS1].
USB-C: “Display connection might be limited”
Windows shows this message when a USB-C display device reports that DisplayPort (or MHL) Alternate Mode was not configured [MS4]. In practice there are three causes, documented by both Microsoft and the dock maker Plugable [MS2] [PL3]:
- The laptop’s USB-C port does not do video. Some USB-C ports carry data only. Check the manual for DisplayPort Alt Mode, Thunderbolt or USB4 display output on that exact port, or try another USB-C port [PL2] [PL3].
- The cable does not carry video. A charging or data cable can fit perfectly and still carry no picture [PL3].
- Something in between blocks Alt Mode. Microsoft’s fix is to connect the dongle directly to the PC, on the USB-C port that supports DisplayPort Alternate Mode, not through an external hub or dock [MS2].
Microsoft also lists “too many other devices or dongles connected to your PC that use a USB-C connection” as a cause [MS2]. Unplug the others and test again.
Through a dock or adapter
A dock adds its own limits. Docks that use DisplayLink or Silicon Motion USB graphics need their driver installed, and Plugable documents a 60 Hz limit for its docks of that type [PL1]. USB-C Alt Mode docks get video from the laptop’s port, so the laptop must support it first [PL2]. See USB-C dock and adapter display limits for lanes, Thunderbolt and MST.
Second or third monitor not detected
First confirm one external monitor works. If one works but two do not, the graphics adapter may not support more monitors; its manufacturer can confirm how many. A computer with one video output supports one external monitor unless you add a dock or a USB display adapter, and a splitter only duplicates one signal [MS1].
Black screen only at a high resolution or refresh rate
If the picture works at 60 Hz and goes black at 144 Hz, the problem is the mode, not the connection itself. Every part must support that exact resolution and refresh combination, and some devices reach a higher refresh rate only at a lower resolution [PL4]. Run the refresh check or read Monitor stuck at 60 Hz.
Sources
- Microsoft Support — Troubleshoot external monitor connections in Windows — Microsoft, checked 2026-10-17 23:58 CEST
- Microsoft Support — Connect Surface to an external display — Microsoft, checked 2026-10-18 00:07 CEST
- Microsoft Support — Fix USB-C problems in Windows — Microsoft, checked 2026-10-17 23:58 CEST
- Microsoft Learn — Windows USB Type-C troubleshooting notifications — Microsoft, checked 2026-10-17 23:58 CEST
- Plugable KB — Can I connect my high refresh rate monitor to a Plugable dock? — Plugable, checked 2026-10-17 23:58 CEST (page updated 2026-09-25)
- Plugable KB — How to determine your USB-C port video capabilities — Plugable, checked 2026-10-17 23:58 CEST (page updated 2026-08-20)
- Plugable KB — "Display connection might be limited" with a USB-C dock or adapter — Plugable, checked 2026-10-17 23:58 CEST (page updated 2023-06-06)
- Plugable KB — How to set the display refresh rate in Windows 11 — Plugable, checked 2026-10-17 23:58 CEST (page updated 2026-08-28)
FAQ
Why does my monitor say no signal when the PC is on?
Usually the monitor is set to the wrong input, Windows is not extending to it, a cable or adapter is faulty, or the port you use does not output video. Check the monitor’s input menu, press Windows logo key + P and choose Extend, then test a different cable and video port.
What does “Display connection might be limited” mean?
Windows shows it when a USB-C display device or dongle could not start DisplayPort (or MHL) Alternate Mode. Microsoft’s fix: make sure the PC, the display and the cable support DisplayPort Alternate Mode, and plug the dongle directly into the PC’s USB-C port that supports it, not through a hub.
How do I reset the graphics driver in Windows?
Press Windows logo key + Ctrl + Shift + B. Microsoft lists it as a fix when a setup that worked suddenly stops; restart if it does not help, and roll back the display driver if the problem started after an update.
Can a splitter give me two extended monitors?
No. Microsoft notes that a splitter duplicates the same signal instead of creating two independent signals, so it cannot extend the desktop. For more external monitors you need more video outputs, a dock or a USB display adapter.
Why does the screen go black only at high refresh rates?
The connection may carry a lower mode but not the one you picked. Every part — computer, dock or adapter, cable and monitor input — must support that resolution and refresh combination. The Display & Connection Solver shows which part sets the limit.