Display 3 won't stay enabled

Windows accepts the third display and then disables it, often indicating a graphics-output or dock-bandwidth limit. Press Windows+P and choose Extend, then open Settings > System > Display and select Detect. Disconnect docks and adapters, power-cycle the monitors, and connect them one at a time. Swap the third monitor’s cable and port with a working monitor; this shows whether failure follows the monitor, cable, or output. Test that monitor on another computer. Lower resolution and refresh rate on screens and turn off HDR. Install Windows updates plus the PC maker’s graphics, USB-C, Thunderbolt, and dock firmware. Check the graphics adapter specification for its maximum displays; a passive splitter duplicates one signal and cannot create another extended desktop. If the third screen works from a direct GPU port but not through the dock, connection bandwidth is the constraint. If every arrangement fails, collect the adapter and dock models for vendor support.