Issue installing Big Sur

Bilgolajon Said:

"Issue installing Big Sur: Is anyone else having issues installing the recent Big Sur 11.2.3 update? I have now downloaded the package multiple times, but some time into the instal process I get a message saying that I have an internet issue and it can't complete as it hasn't downloaded? [...]Any thoughts/suggestions as to what to do, especially since Apple aren't interested in providing chat support as I don't have a subscription for such a question on chat!!"

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Use Ethernet:

Try using Ethernet, as it would be a hardwired connection, thereby making it more reliable. Connect your Mac directly into the router. If your Mac has no builtin Ethernet port, then this is the adapter that you may need to use: Belkin USB-C to Gigabit Ethernet Adapter - Apple

Bilgolajon Said:

"Issue installing Big Sur: Is it possible to download the update and save that locally so that I am not constantly re-downloading the 3Gb package each time?"

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Also, try Recovery Mode:

Hold Down: [Option/Alt + Command + R] upon boot. It upgrades to the latest version of macOS that is compatible with your Mac.

Bilgolajon Said:

"Thank you TheLittles, eventually I went to the Recovery Mode option and whilst this took several hours to complete, it has installed the latest version of Big Sur. [...]it is still a mystery as to why a standard update instal would not work[...]"

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Possibly a Glitch:

You are welcome. It was probably a glitch or a system error of sorts, and reinstalling the macOS may fix that from here on out. So, what to do...

Reinstall the macOS:

If that application cannot be opened, then you may need to reinstall the macOS.

1. First, Back up your Mac:

Create a Time Machine backup of your Mac, so that you can have something to restore your Mac from, should anything go wrong with the transfer.

2. Then, Reinstall the macOS:

Nothing would be deleted. It's just that items that have become corrupted or deleted, would be replaced or reinstalled back to where they should be. Go Here: How to reinstall macOS from macOS Recovery - Apple Support

Bilgolajon Said:

"Issue installing Big Sur: Thanks for the suggestion - I gave it a go and had exactly the same result..."

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You are welcome.

Three Thoughts:

A. Try it in Safe Mode.

When you boot in Safe Mode, login items do not open at log in, certain preferences are set aside, and damaged system files (i.e. caches) are fixed. To boot up in Safe Mode [Hold Down: the shift key upon boot].

B. Use a New Admin User:

Create a new administrator for temporary user, and see if you can install with that user. Once all is installed, login to the normal user, and delete this user you just created for the install.

C. Network Options:

If you are on your own network, then restart your router (power off the router for 30 seconds, and then power it pack on). If you are on a public LAN, then try another network.