Late 2013 MacBook Pro, macOS Catalina 10.15.7, can't upgrade to macOS Big Sur

My macbook Have a late 2013 MacBook Pro, currently running macOS Catalina 10.15.7.

This device is supposed to be compatible for upgrade to macOS Big Sur, per publications and the App Store, however when selecting 'System Preferences,' it states "Your Mac is up to date -- macOS Catalina 10.15.7".

And...of course, attempts to "get" macOS Big Sur directly from the App Store fail and give the message "Update not found. The requested version of macOS is not available".

Sincerely,

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