Now, check your external monitor with the mac display. It should work properly. In some cases, using the sleep and wake method will fix your issue of mac external monitor not working after an update, but if that doesn’t work, you can try other methods.
Fix 4: Check Cables and Adaptors
Whenever you connect your mac to an external monitor, you might experience problems with the external monitor not displaying or not detecting properly if the cables and adaptors are damaged or loose.
Fix 5: Detect External Display
- Click on the Apple logo and then on System Settings.
- From the left side menu, select Display.
- Place the detect display button in place of the night shift button by holding down the option key.
- When Detect Display is displayed, click on it to wake it up.
The issue of the external monitor not being detected or not recognising will be solved once you detect and wake up the external display on your mac.
Fix 6: Reset SMC For MacBook Pro or Air With T2 Chip
- Using the Apple menu, select Apple logo > Shutdown > Wait until your Mac shuts down.
- You must hold down the Control + Option + Shift keys for 10 seconds before you can select touch ID or power button.
- Wait for your mac to turn on after 10 seconds, then turn it on after 10 seconds.
Fix 7: Change screen resolution
If your external monitor does not scale well on macOS Sonoma or you want to customize the screen resolution, follow these steps:
- Select System Settings from the Apple menu.
- Press the Option key and select “Large text” or “More space.”
- Now, you should be able to choose from a variety of resolution options.
Fix 8: Update your Mac
Macs that don’t detect external displays could also be a result of bugs in the current version of macOS. It is possible that the bug has been fixed in a newer release. If there is a new update available for your Mac, make sure you install it.
MacOS Sonoma not detecting external monitors can be fixed by checking for updates under Apple menu > System Settings > General > Software Update.
Fix 9: Update the hub driver or software
It is very likely that the driver for the USB hub or adapter that you use for your monitor does not work with the updated macOS yet, which means that Macs are not able to detect external displays on macOS Monterey, Ventura, Sonoma and other recent versions.
To see if a new driver or software is available, you should check the official hub website or the support page, such as DisplayLink Manager Graphics Connectivity (1.6). If there is an update for the driver, install it. MacOS Sonoma users may also find this useful in the event that the “Detect Displays” button does not appear.
So, that’s all we have for you on how to fix the macOS Sonoma Not Detecting External Monitor. It’s our hope that this guide has helped you. In the meantime, in case you need more help, comment below and let us know