You are not alone, if you have just experienced the case of YouTube not opening or loading videos on Mac, as this problem has been reported by other users.
In general, users have reported the case of YouTube being stuck, taking forever to load and coming up with an empty blank page or white/grey boxes when it was accessed using the default Safari browser on Mac.
This was happening while the Safari browser perfectly capable of accessing other websites and there was no indication of the Wi-Fi network being weak or going through connectivity issues.
YouTube Not Opening on Mac Safari Browser
Before going ahead with other troubleshooting steps make sure that the Safari browser on your MacBook is not going through network connectivity problems by trying to access other websites.
If the issue is only related to YouTube, you should be get YouTube working properly on your MacBook by using the following troubleshooting steps.
1. Clear Browsing History & Cache
Start by clearing the Safari browsing history on your Mac to rule out this problem being caused due to an error page being stored in the browser cache.
For the steps to clear browsing history, you can refer to this guide: How to Clear Browsing History on iPhone & Mac.
This will clear all your Safari Browsing history, including the cached error pages, which might be causing this problem on your Mac.
2. Uninstall Ad Blocking Extension
A common reason for YouTube not working properly is due to use of Ad blocking extensions or plugins.
1. Open the Safari Browser on your MacBook.
2. Click on the Safari tab in the top-menu bar and select Preferences… in the drop-down menu.
2. On the next screen, go to Extensions tab > select the Ad Blocking Extension and click on the Uninstall button.
If you are unable to Uninstall the Ad Blocking extension, you can do it by going to the Applications folder on your MacBook (the next method)
3. Remove Ad Blocker from Extensions Folder
Certain Ad Blocking extensions can be sticky and prevent deletion while the Safari browser is being used.
1. Close the Safari browser on your MacBook.
2. Right click on the Safari Icon in the Dock and select the Quit option.
3. Next, open the Finder on your Mac and go to the Applications Folder.
4. On the Applications folder, right-click on the Ad Blocking Icon and select Move to Trash option.
5. You can clear the Recycle bin to permanently remove the Ad blocking extensions from your Mac.
After disabling the extensions, relaunch Safari browser and see if YouTube is now working properly on your Mac.