how to download macOS big sir 11.6.8

If the computer is already running Big Sur - the normal method would to use the System Preferences >> Software Update Applet.

User profile attached to your posting above is showing the computer is running MacBook Pro 15″, macOS 11.6 Big Sur

Is there an issue occurring when attempting Software Update Applet ?

when I use preferences to check for software updates it goes into an endless spin, never finding the update. I shut down my computer tried again, same response. But every time I connect my iPhone to my computer I get the message that the software update is required in order to connect. My computer has a ton of memory so that is not the issue

Hi,

See: How to get old versions of macOS - Apple Support

Try again while in Safe Mode.

How to use safe mode on your Mac - Apple Support