Mac -Here are some troubleshooting steps you can try:
Check the connections: Make sure that your external monitor is properly connected to your Mac. Check the cables and connectors to ensure that they are firmly attached and not damaged. If you’re using an adapter, try using a different one.
Restart your Mac: Sometimes a simple restart can fix the problem. Restart your Mac and see if the external monitor is detected.
Check the Display settings: Open System Preferences and click on Display. Make sure that the external monitor is detected and set as the primary display. If it’s not, click on Detect Displays to see if your Mac can find it.
Reset NVRAM/PRAM: Resetting the NVRAM (or PRAM on older Macs) can fix some display-related issues. To reset NVRAM, shut down your Mac and then turn it back on while holding down the Command + Option + P + R keys until you hear the startup sound twice.
Try Safe Mode: Booting into Safe Mode can help diagnose and fix issues that may be causing the external monitor not to be detected. To enter Safe Mode, restart your Mac and hold down the Shift key until the Apple logo appears.
Update macOS: Make sure that your Mac is running the latest version of macOS Ventura. Check for updates by going to System Preferences > Software Update.
Try a different monitor: If none of the above steps work, try connecting a different external monitor to your Mac to see if the issue is with the monitor or the Mac.
If none of these steps work, you may need to contact Apple support for further assistance.