OS software update

Apple differentiates updates (what you are checking) from upgrades. Updates are minor changes and fixes and are expected to be compatible changes. Upgrades are larger and more involved, and can and variously do disrupt some apps, and can add or remove various features. Upgrades must be specifically requested, as app stuff can break.

Please post the model and model year of this Mac. The Mac model and model year are displayed by 🍎 > About This Mac. With both the model and model year re-posted here, we can then provide you with your upgrades options, as determined by the specific Mac and model year you have.

Or you can learn more about this upgrade yourself: How to get old versions of macOS - Apple Support

Have a complete and current backup before performing any upgrade.

There can be other upgrade considerations, depending on which macOS version you (can and do) upgrade to.

I, too, have this problem and am unable to update from High Sierra. Here is the info you asked for in order for you to help me.

Hope this helps you help me :D

[Image Edited by Moderator to Remove Serial Number]


That iMac tops out at High Sierra, and cannot be upgraded to a newer version.

Image reposted without the serial number:

High Sierra is the latest version you can run.