Not all macOS updates are supported for the MacBook Air 2015 model.
Not all macOS updates are supported for the MacBook Air 2015 model.
I just reinstalled my sister's Mac and set it up as a MacOS system. After that, I wanted to add Microsoft Word and Pages, which needed an update to a newer version of MacOS. When I checked for updates, it showed no available updates for my MacBook Air. Apple Support mentioned I could upgrade the operating system.
Confirm if it's a 2015 Air model. If yes, check if you can access recovery options and try that. Also, visit the app store and look for Catalina—it should appear and let you install it.
Check the link in the App Store for the update. After opening it, you'll find the download option for the update tool. Apple confirms the 2015 MacBook Air works with Monterey: https://support.apple.com/en-us/HT212551
I located it, though the App Store acts oddly. The password field is correct, and the phone displays a verification code. However, the App Store rejects it, insisting the input was incorrect. (Phone confirms login.) If you leave the Password column blank and press Enter three times, it forces the App Store to log in, but downloading still fails. I’ll send it to a technician tomorrow. It looks like a software problem. Battery and other functions work fine.
It could be tough to upgrade to a newer Mac OS with that older version due to constraints of the existing one. Certificate problems also meant needing to adjust the system date for certain updates to function properly. A simpler approach would be creating a Catalina USB installer on another machine and performing a clean install.