Why won’t my older BenQ monitor work as a second display?

Because the BenQ XL2411Z is an older 1080p display, avoid sending it a high refresh rate or an unusual resolution during testing. In Windows display settings, select the BenQ, choose 1920×1080, and set it to 60 Hz first. Once it displays properly, you can try higher supported refresh rates.

The cable is still the most likely weak point, especially because older monitors can be picky about DisplayPort-to-HDMI connections. Confirm that the cable runs from the graphics card’s DisplayPort output to the BenQ’s HDMI input—the cable must be used in that direction. If selecting HDMI and lowering the refresh rate doesn’t help, try a different DP-to-HDMI adapter or cable, preferably one explicitly supporting an active DisplayPort-to-HDMI conversion.

Check the monitor’s input source directly with its buttons. “No Cable Connected” often means it is checking DVI while the signal is arriving through HDMI. I’d also shut down the PC and monitor, unplug the BenQ for a minute, reconnect the cable, then boot again. If possible, test the BenQ with another HDMI source to rule out a faulty HDMI input.

The OLED and non-OLED monitors are completely fine to use together; that has no effect on whether the second display works. Since Windows recognizes the BenQ, the graphics card is probably reading its identification data, but the monitor may be listening to the wrong input. Open the BenQ’s menu and manually select HDMI rather than leaving it on Auto or DVI. Also make sure Windows is set to Extend these displays and try forcing the BenQ to 1920×1080 at 60 Hz.