Go to System Preferences > Displays, click Scaled and hold down the Option key to show and select the Detect Displays button. Go to System Preferences > Displays and check the resolution and brightness settings. Also, check the display cable connections, and update adapter software if applicable.
Why is my 2nd monitor not working on Mac?
Go to System Preferences > Display and try selecting a different resolution. If that still doesn’t work, try restarting your Mac in safe mode and then reset the display resolution to defaults. Another option is to reset the Mac’s NVRAM and SMC.
Why is my 2nd monitor not displaying?
Causes of Second-Monitor Problems Secondary-display problems usually come down to a few basic causes: The computer can’t support the display in color depth, pixel count, or interface options. The monitor’s cable is damaged or malfunctioning. The computer’s display drivers aren’t handling the secondary display properly.
Why does my second monitor say no signal Mac?
Use a MultiPort Adapter As a quick reminder, M1 Macs can’t handle two external monitors. They natively support just one monitor. So, if you’re getting a “No Signal” prompt when using a two-monitor configuration with your M1 MacBook, buy a Hyperdrive Dual HDMI Adapter to work your way around this limitation.