No display signal

Confirm the monitor is powered and on the intended input

A “No Signal” message means the display is not receiving a usable video signal on the selected input at that moment. It does not by itself show whether the monitor, cable, dock, or computer is at fault. Check the power indicator and use the monitor’s input control to select the port that the cable actually uses. If the OSD appears, the monitor can display its own menu even though the source image is missing.

Verify that the computer is awake and set to extend or mirror its display. A sleeping laptop, closed lid, or disabled external display can leave a healthy monitor waiting for input. Wake the computer and open its display settings before changing monitor firmware or buying a cable.

Trace the cable path end to end

Follow the signal from the computer’s video output to the monitor input. Confirm that the cable is connected to an active graphics output; some desktop systems have both motherboard and graphics-card ports. Reseat both ends while avoiding side pressure on the connector. If a dock, adapter, KVM, or receiver is involved, test the computer directly to the monitor with a supported cable.

USB-C needs special care: the host port must support video output, and the cable must carry the required video mode. Dell’s support guidance specifically identifies host-port capability as a cause of no display over USB-C. Charging or file transfer alone does not prove that the same port carries DisplayPort video.

Compare one variable at a time

Try a second monitor input with a known-good cable, or try the current cable with another compatible source. Change only one item per test. If direct connection works but the dock path does not, check the dock’s port and resolution limits and its firmware. If the monitor reports no signal with multiple sources and cables, run its model-specific built-in self-test or diagnostic.

Do not force an unsupported resolution or refresh rate. If the computer output was set to a mode outside the monitor’s timing table, use safe mode or another display to restore a supported setting. Record the mode that failed and the mode that works.

Use the test result to choose support

If the monitor’s self-test displays normally, the panel can generate its own image in that test, so investigate the input path, host, cable, or dock next. If the self-test itself is abnormal, provide that result to monitor support. Dell’s BIST instructions apply to supported Dell models; use the exact procedure and do not transfer its button sequence to other brands.

Share the monitor model, host model, dock, exact ports, cable type, operating system, power-light behavior, and test result. Photograph the no-signal message. This lets support separate a missing source from a monitor fault without guessing from the phrase alone.

Check the host output mode after sleep or docking

Laptops can change display behavior when a lid is closed, a dock is connected, or power-saving resumes. Open the laptop and use the operating system’s display controls to detect or enable the external monitor. Confirm that the selected resolution and refresh rate appear in the monitor’s supported timing list. If a dock was just attached, reconnect its host cable and verify that it receives the power or firmware state required by its manual. Record whether the monitor’s no-signal message appears before or after the operating system detects it.

Check input selection after host wake

Some monitors do not switch inputs immediately when a computer wakes from sleep or a dock reconnects. Use the OSD to choose the active port, then wait for the host to detect the display. If the image returns only after changing input, note that sequence and check the manual for automatic input selection or power-saving behavior. Do not mistake delayed detection for a panel failure without testing another source.