I have a 2008 computer using OS Yosemite. Why can't upgrade?

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.  For Best results use Safari to commence the download as Others may not work.

Safari will open a redirect and open the Apple Store where the download can commence

OS X El Capitan - Technical Specifications this is the last version this computer Qualifies to run

Make Time Machine Backup  is very useful and can be used to Revert to Previous Working macOS

Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal  operation of the OS and may even Corrupt the OS requiring a Reinstallation

Use Safari to download macOS on your Mac jomaso507 ; Yosemite

Safari uses these links to find the old installers in the App Store. After you download the installer from the App Store, the installer opens automatically.

• macOS Big Sur can upgrade Catalina, Mojave, High Sierra, Sierra, El Capitan, Yosemite, Mavericks
• macOS Catalina can upgrade Mojave, High Sierra, Sierra, El Capitan, Yosemite, Mavericks
• macOS Mojave can upgrade High Sierra, Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion
• macOS High Sierra can upgrade Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion

Safari downloads the following older installers as a disk image named InstallOS.dmg or InstallMacOSX.dmg. Open the disk image, then open the .pkg installer inside the disk image. It installs an app named Install [Version Name]. Open that app from your Applications folder to begin installing the operating system.

• macOS Sierra can upgrade El Capitan, Yosemite, Mavericks, Mountain Lion, or Lion
• OS X El Capitan can upgrade Yosemite, Mavericks, Mountain Lion, Lion, or Snow Leopard
• OS X Yosemite can upgrade Mavericks, Mountain Lion, Lion, or Snow Leopard

Published Date: December 14, 2021