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Big Sur software update not working, won't download.

Software update started downloading the 10.15.1 update on the first day it was available. It stalled during that initial download part way through. Now, when I retry the update the download won't start downloading. I get a status bar with no progress or additional text.


I have plenty of available space and I'm on a robust network connection.

MacBook Pro (2020 and later)

Posted on Aug 5, 2021 11:32 AM

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Question marked as Top-ranking reply

Posted on Aug 5, 2021 4:54 PM

Check in Applications Folder and see if there is an " Install Big Sur " if one exists. If Yes, Drag and Drop to Trash and empty Trash.


If this update is for Big Sur 11.5.1 - the error message can be misleading. There are factors like poor Wifi connection, slow wifi connection, too many other people downloading at the same time and Apple Severs are overloaded, Software on the computer interfering with the download process, running behind a VPN and or / if via wifi too many Other devices using the wifi at the same time reducing the Bandwidth to you computer.


Best Results are via Ethernet Cable to Router


There are several ways to download the Big Sur 11.5 .1update. 


1 - Connect to Router via Ethernet connection and restart the computer in Safe Mode and then open the Apple Apps Store and get the Full Installer of Big Sur. It will be the 11.5 version and once downloaded run the installer from the Applications folder.


2 - Resart the computer in Recovery Mode ( INTEL Command + r ) and choose Reinstall macOS. It too will download the full Installer and commence the installation. For M1 CPU the Recovery Mode is Here


3 - This method may seem unnecessary but sometimes the Router Restart clears Network issues from ISP to Apple Servers


Shutdown Router. Shutdown computer and disconnect all External Drives. Restart Router. Connect to Router via Ethernet Cable. If via Wifi - Disconnect all other Devices using the Wifi - want the Maximum Bandwidth only for this computer. Restart computer in  Safe Mode. It does a Repair Disk, Clear System Cache files and only load Apple Software, extensions and Fonts. Will load slowly - Normal. Once Logged in - open Apple Apps Store and  Get the Full Version of Big Sur. It will take some time and several pauses will occur - normal. Countdown clock may say 15 minutes but in Real time may be 30 minutes. Same goes for clock at 10 minutes could be 20 minutes in Real time. Eventually , Full Installer will download and a New Application in Applications Folder will present called Install Big Sur. Stop there and perform a Time Machine Backup. If desired - have an External Drive - Copy & Paste the Install Big Sur Application to external drive for future usage - making a Bootable Installer. Now run the Installer.


Have found this method more reliable than the Software Update which is very iffy at best


Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation.

3 replies
Question marked as Top-ranking reply

Aug 5, 2021 4:54 PM in response to kmac17

Check in Applications Folder and see if there is an " Install Big Sur " if one exists. If Yes, Drag and Drop to Trash and empty Trash.


If this update is for Big Sur 11.5.1 - the error message can be misleading. There are factors like poor Wifi connection, slow wifi connection, too many other people downloading at the same time and Apple Severs are overloaded, Software on the computer interfering with the download process, running behind a VPN and or / if via wifi too many Other devices using the wifi at the same time reducing the Bandwidth to you computer.


Best Results are via Ethernet Cable to Router


There are several ways to download the Big Sur 11.5 .1update. 


1 - Connect to Router via Ethernet connection and restart the computer in Safe Mode and then open the Apple Apps Store and get the Full Installer of Big Sur. It will be the 11.5 version and once downloaded run the installer from the Applications folder.


2 - Resart the computer in Recovery Mode ( INTEL Command + r ) and choose Reinstall macOS. It too will download the full Installer and commence the installation. For M1 CPU the Recovery Mode is Here


3 - This method may seem unnecessary but sometimes the Router Restart clears Network issues from ISP to Apple Servers


Shutdown Router. Shutdown computer and disconnect all External Drives. Restart Router. Connect to Router via Ethernet Cable. If via Wifi - Disconnect all other Devices using the Wifi - want the Maximum Bandwidth only for this computer. Restart computer in  Safe Mode. It does a Repair Disk, Clear System Cache files and only load Apple Software, extensions and Fonts. Will load slowly - Normal. Once Logged in - open Apple Apps Store and  Get the Full Version of Big Sur. It will take some time and several pauses will occur - normal. Countdown clock may say 15 minutes but in Real time may be 30 minutes. Same goes for clock at 10 minutes could be 20 minutes in Real time. Eventually , Full Installer will download and a New Application in Applications Folder will present called Install Big Sur. Stop there and perform a Time Machine Backup. If desired - have an External Drive - Copy & Paste the Install Big Sur Application to external drive for future usage - making a Bootable Installer. Now run the Installer.


Have found this method more reliable than the Software Update which is very iffy at best


Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation.

Aug 5, 2021 11:52 AM in response to kmac17

How much free space do you have on your boot drive? If it's less than 50 GB you'll have problems with the download and install.


Also try going to the App Store and search for macOS Big Sur. Click on the View button to get to this view:



This will be the full installer at the latest version. I've had better results going thru the App Store than directly thru Software Update.


Aug 5, 2021 9:35 PM in response to Old Toad

As I mentioned. I have plenty of space, over 300gb at the moment. When I select the update it never starts downloading and there are no error messages what so ever. I have 11.4 currently and never loaded 11.5 (was on a vacation when it came out...) I don't run any junk software as a rule. My experience is that if you avoid the junk sites, you don't need the junk cleaners. I've usually found that the apple side of the equation is usually where the slowness happens versus my side. I think my computer was a little too early to the download party and that's why the download failed initially.


Downloading from the App Store is currently running. We'll try that route and I'll report back.


Thanks, Kevin.



Big Sur software update not working, won't download.

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