Windows does not detect a second monitor

Establish the scope

Open Display settings and distinguish a missing numbered display from a listed screen that is blank. If Windows lists it, check Extend mode and the monitor input. If it is absent, compare a direct cable without the dock and test the monitor on another source to narrow connection versus display faults.

Apply the safer fix first

Select the correct monitor input, test a known-good direct cable, then choose Detect in Display settings.

Investigate the cause

Power-cycle the dock, reduce adapters, and update graphics and dock drivers from their makers. Test the monitor on another source.

Protect the recovery path

Keep one readable display while changing the arrangement. Safely remove any dock-connected storage before disconnecting or power-cycling the dock.

Verification

• Confirm both displays appear in Settings and move a window onto the intended extended desktop.
• Reconnect the original cable or dock arrangement and test sleep/wake if that triggered the missing display.

When to stop

Do not continue with broader resets when ports are damaged, firmware screens fail, or the monitor fails another source. Preserve the observations already collected and use the device maker, network administrator, Microsoft support, a qualified repair technician, or data-recovery help according to the evidence.

Review the safe troubleshooting workflow before any broader recovery step.