Check this first
The short answer
Open Settings → System → Display and look for a second numbered display. If it exists, compare Windows + P → Extend and select the monitor’s actual HDMI or DisplayPort input. If absent, use Detect and compare a direct connection, cable and port.
- Check monitor power and that its selected input matches the connected socket.
- Select Windows + P → Extend and inspect whether Display settings shows a second screen.
- If undetected, compare a direct connection without the dock, then another compatible cable.
Choose your next check
Start with the row that matches your situation. Change one setting at a time so you can tell what helped.
| What you see | What to compare | Go to |
|---|---|---|
| Display settings shows screen 2 but it is black | Compare Windows + P mode and the monitor’s input selection. | Step 1 |
| Detect still cannot find screen 2 | Compare cable, direct connection and the monitor on another PC. | Step 2 |
| Only the dock or USB-C path fails | Verify video support across the PC port, dock and cable. | Step 2 |
| It stopped after a graphics-driver update | Record before/after versions and Device Manager status. | Step 3 |
Check in this order
Continue this issue
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Step 1: Check whether Windows has detected the monitor
- Open Start → Settings → System → Display. Look for numbered displays 1 and 2; if present, select the affected screen.
- Record your current projection mode, then press Windows + P and select Extend. PC screen only does not extend the desktop to the second display.
- Open the monitor’s own input menu and choose the HDMI or DisplayPort socket where the cable is connected. Compare whether No signal changes to an image.
- Expected result or what you learned
- Windows shows both displays and the pointer can move onto the second screen in Extend mode.
- If something is wrong or unclear
- If no second display is listed, use Step 2. If detected but still reporting No signal, inspect the selected input and cable.
- How to undo changes
- Restore the previous Windows + P option, such as Duplicate or PC screen only, and the monitor’s previous input if needed.
Step 2: Compare detection and the connection path
- Open Settings → System → Display → Multiple displays → Detect. Record the message and number of displays.
- If absent, bypass the dock or adapter and connect PC to monitor directly. Compare another compatible cable and another supported port separately, keeping the same monitor.
- If another PC is available, compare the monitor there. For USB-C, verify that the exact port, cable and dock support video output; the connector shape alone does not establish it.
- Expected result or what you learned
- Direct-only success prioritizes the intermediate dock, adapter or cable. If another compatible PC also fails, investigate the monitor side first without treating that single test as a definitive fault diagnosis.
- If something is wrong or unclear
- If direct detection fails on this PC but works on another, use Step 3 for the original PC’s graphics driver and port investigation.
- How to undo changes
- Shut down or disconnect safely according to the devices’ instructions before restoring wiring. Restore the previous display mode.
Step 3: Check the graphics driver when the problem followed an update
- Search for Device Manager → Display adapters. Open the actual GPU’s Properties → Driver and record its version and date.
- If the failure followed an update and the previous driver is retained, consider Roll Back Driver. Save work first, restart when required and check whether Display settings again shows both screens.
- If the button is unavailable, the previous driver may not be retained. Check the GPU or PC manufacturer’s compatible supported package; on a work PC consult the administrator.
- Expected result or what you learned
- If changing the version restores detection, the driver change may have contributed. Record the versions and result.
- If something is wrong or unclear
- If rollback is unavailable or has no effect, give the manufacturer your model, port and direct-connection results. Do not repeatedly uninstall display adapters.
- How to undo changes
- If another problem appears, ask about the manufacturer’s compatible current driver and restore the recorded projection mode and monitor input.
When to ask for help
Record monitor, PC, dock and cable models, a connection diagram, Detect results, other-PC/direct comparisons and GPU-driver version. If the main PC screen is black too, this guide’s usable-screen assumption does not apply; seek startup or display help for that condition.
FAQ
Why does Windows show screen 2 while the monitor says No signal?
Check the Windows projection mode and the monitor’s selected physical input. Compare cables and any adapter one at a time.
What if I cannot choose Extend?
Check the cable and input first, then use Detect in Settings. If using a dock, compare a supported direct connection as well.
Sources
English adaptation preserving the Japanese guide’s diagnostic branches, steps, outcomes, undo instructions and official sources. Official guidance was reviewed; these comparisons are not claims of testing every cable, dock or device. Confirm the exact model and required features. Ask the administrator before changing a managed PC.
Microsoft: external monitor connectionsMicrosoft: using multiple monitorsMicrosoft: USB-C connection and feature compatibility