upgrade MacBook Air 13" (mid-2013) from Sierra to a newer Mac OS

Why can't I upgrade my MacBook Air 13" (mid-2013) from Sierra to a more recent OS? When I search for upgrades in the App Store or through System Preferences / About this Mac, no upgrade options are shown. And when I click on the link on the Apple Support site to download any of the older Mac OS versions (Big Sur, for example: https://apps.apple.com/us/app/macos-big-sur/id1526878132?mt=12), I just get a blank page. No download begins, and the App Store doesn't open.