Why does my monitor say 'no signal' when my computer is on?

No signal with the computer running means the monitor is not receiving a video output from the GPU. The most likely causes in order of frequency: wrong input source selected on the monitor (fix with the OSD input selection button), loose or wrong cable (try reseating both ends and swapping cable types), GPU not outputting to the connected port (check Display Settings with Win+P), or GPU driver issue. A black screen that shows the desktop briefly before going dark is different — that is typically a driver crash or refresh rate mismatch, not a physical connection issue.

My monitor flickers at 144Hz but works fine at 60Hz — what is wrong?

Flickering at high refresh rates but not lower rates is almost always a cable bandwidth issue. At 144Hz, the cable must carry significantly more data per second than at 60Hz. An HDMI cable that is marginal for the required bandwidth passes at 60Hz but fails at 144Hz. For 1440p 144Hz: use DisplayPort 1.4 instead of HDMI — DisplayPort handles higher bandwidth more reliably for monitor connections. For HDMI: replace with a certified HDMI 2.0 cable (rated 18Gbps) for 1440p 144Hz, or HDMI 2.1 (48Gbps) for 4K 120Hz+. Also check whether VRR (G-Sync/FreeSync) is causing the flicker — disable it temporarily to isolate.

How do I fix a monitor that keeps going to sleep?

A monitor that repeatedly goes to sleep while in use is usually caused by: Windows Power Settings set to turn off the display too quickly (Settings > System > Power > Screen and Sleep — set to 'Never' during troubleshooting), a loose video cable that intermittently loses signal causing the monitor to sleep, or a failing cable or GPU port. Differentiate by checking whether the monitor's power LED goes from white (active) to amber (standby) when it sleeps — amber indicates the monitor is receiving no signal, which points to a cable or GPU issue rather than Windows settings.

Why does my 4K monitor only show 1080p?

A 4K monitor displaying at 1080p means either the cable cannot carry 4K signal or Windows resolution settings are capped. Check the cable first: HDMI 1.4 cannot carry 4K at 60Hz (only 4K at 30Hz), and some USB-C cables do not support 4K. Switch to DisplayPort 1.4 or HDMI 2.0+. In Windows Display Settings, manually set the resolution to 3840x2160 (4K). If the 4K resolution option does not appear in the dropdown, the cable or GPU output does not support 4K at the required refresh rate — lower the refresh rate to 30Hz temporarily to confirm 4K appears, then resolve the cable issue.

Monitor Not Displaying: 8 Fixes for No Signal, Black Screen, and Flickering

Monitor display problems fall into two categories: no signal (the monitor gets no video) and incorrect display (the monitor shows something but it is wrong). Each has a different troubleshooting path.

No Signal / Black Screen

Start with the physical connection: cable type, port selection on the monitor's OSD, and whether Windows sees the monitor in Display Settings.

Flickering

Replace the cable first. If that does not fix it, disable VRR (G-Sync/FreeSync) temporarily to determine whether the issue is cable bandwidth or VRR handshake.

Wrong Colors / Resolution

Verify the Windows color space setting (RGB, not YCbCr) and confirm the GPU driver is sending the correct resolution and refresh rate.

For monitor selection guidance, see how to choose a monitor.