I kept getting an error message that my internet connection failed when trying to download the update. I have a MacBook Air 2019 and this is what worked for me after trial and error: Cleared cache and cookies in browser Restarted in safe mode While in safe mode, I deleted old files and apps that I don't use and this seemed to move the download along I kept my Mac charging while it was downloading and installing It took about 20-25 minutes to complete.