Symptoms
- Monitor is on and showing its own logo or backlight, but the OS doesn't list it
- Display Settings shows only one monitor even with two connected
- Monitor worked before but stopped appearing after an update
- 'Detect' button in Display Settings doesn't find it
Likely causes
- CommonCable not fully connected or faultyA loose or bad cable prevents the OS from even recognizing a display is present.
- CommonWrong input selected on the monitorThe monitor may be waiting on a different input than the one connected.
- CommonGraphics driver issueAn outdated or corrupted driver can fail to enumerate a connected display.
- PossibleMonitor's EDID not being read correctlyA cable, adapter, or port issue can prevent the OS from reading the monitor's identifying data.
What to do
- Confirm the monitor is powered on and set to the correct input using its own onscreen menu.
- Reseat the video cable at both ends, and try a different cable and port if available.
- Click 'Detect' in Display Settings (Windows) or 'Detect Displays' (Mac) after confirming the cable is connected.
- Update the graphics driver from the manufacturer's website and restart the computer.
- If using an adapter (USB-C to HDMI, DisplayPort to HDMI, etc.), test with a direct native cable if possible to rule out the adapter.
- Test the monitor on a different computer to confirm the monitor itself is functioning and can be detected elsewhere.
Tools and parts
- None
Replacement video cableSearch: “DisplayPort or HDMI cable”
When to call a pro
If the monitor isn't detected on a different computer either, with a known-good cable, the monitor's input board or connector may be faulty and should be checked by a technician.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.