otter2mn Said:
"upgrading from OS X El Capitan: How to upgrade from OS X El Capitan. When we upgrade from the apple menu, it opens the app store and says no updates available. I don't think the computer has been updated ever! It's not working properly. Any advice on how to upgrade!"
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Upgrade to High Sierra First:
If you want to upgrade, the Catalina*** may be the Highest you can go. So, to do that, you need to upgrade to High Sierra first, then proceed with the upgrade. Use this Link: How to Get Old Versions of macOS - Apple Support
***macOS Catalina is Compatible with these Computers - Apple Support