External Monitor/Display Not Working on Mac After macOS Sonoma

After updating your macOS to latest version macOS Sonoma from macOS ventura or monterey to macOS sonoma and after connecting external monitor to macbook pro or air is not working even though connecting properly with external monitor then you can easily fix this issue of external monitor not displaying or not working after macOS update to macOS sonoma easily. So, let’s see in detail below.

When you connect your macbook pro or air to an external monitor and its not recognising or not detecting external monitor then you need to restart your mac and disconnect all cables connect mac to external monitor again and check.

External Monitor/Display Not Working on Mac After macOS Sonoma

Below methods will help you fix mac external monitor not after after updating mac to macOS sonoma.

Sleep and Wake Up your MacBook pro or air

Step 1: Click on apple logo on top corner and click on sleep option and wait for your mac to go to sleep mode.

Step 2: Now, wait for 30 seconds and then click on trackpad or any key on your macbook pro or air keypad and wake your mac.

Now, go ahead and check with the mac display on your external monitor and it should work fine. Sometimes, the sleep and wake method will work and your issue of mac external monitor not working after update will be fixed and if not you can try different methods as well.

Check Cables and Adaptors

If your cables and adaptors get damaged or have loose connection, then you can experience this issue of external monitor not displaying properly or external monitor not detecting issue when connecting mac to external monitor.

Detect External Display

Step 1: Click on Apple logo and click on System settings.

Step 2: Click on Display from left side menu

Step 3: Hold down option key and make detect display button appear in place of Night shift button.

Step 4: After displaying Detect Display -> Click on Detect Display and this will wake up Detect Display.

Once your detect external display detects and wakes up then you will be able to connect your mac to external monitor and your issue of external monitor undetected or not recognsing issue will be fixed.

Reset SMC

If you are using mac without T2 chip then follow below steps.

Step 1: First shutdown your mac -> Click on Apple logo and click on Shutdown and wait for the mac to shutdown.

Step 2: Press and Hold down shift key + Control Key + Option + Power button or touch id for 10 seconds.

Step 3: After 10 seconds, release the buttons and then press power button or touch id and turn on your mac.

This will reset your smc if you’re having a mac without T2 chip.

Enable Mirror Display

Step 1: Click on Apple menu -> Click on System Settings

Step 2: Click on Display from left side menu

Step 3: Click on Arrangement tab

Step 4: Select the check box -> Mirror Display and enable mirror display.

 Now, After enabling Mirror display, then go ahead and check with external monitor display on mac and it should work fine.

Reset SMC For MacBook Pro or Air With T2 Chip

Step 1: Shutdown your mac from apple menu -> Apple logo -> Shutdown -> Wait for mac to shutdown.

Step 2: Press and Hold Control + Option + Shift key press power button or touch id for 10 seconds.

Step 3: Now, after 10 seconds turn on your mac and wait for your mac to turn on.

Mac with Apple Silicon

If you are using a mac with Apple silicon then to reset smc then you need to just restart your macbook pro or air from apple menu -> Click on Apple logo -> Click on Restart and wait for your mac to restart.

What to Do if Mac Doesn’t Recognise External Monitor

If your mac is not recognising external monitors then you need to check with cables and adaptors and check if they got damaged or if cables are loosely connected and check with external monitor display settings and unplug and plug back cables again and check.

Why is my Mac not Detecting Second Monitor After Update?

This can happen due to software glitch or it can be an issue with connecting cables or adaptor and you need to unplug and connect cables and adaptors again and check external monitor display settings on mac.