Can't update iMac

Hello, SISAVATH241.

How to Upgrade to  macOS 10.13 High Sierra:

❗️– Backup your data. (You’ve been warned.)

Learn How to Back up your Mac with Time Machine:

click > https://support.apple.com/en-us/HT201250

📚 – Check Compatibility of your Mac with newer versions of macOS.

Learn how to upgrade macOS:

click > https://support.apple.com/en-us/HT211683

These Mac models are compatible with macOS High Sierra:

• MacBook (Late 2009 or newer)

• MacBook Pro (Mid 2010 or newer)

• MacBook Air (Late 2010 or newer)

• Mac mini (Mid 2010 or newer)

• iMac (Late 2009 or newer)

• Mac Pro (Mid 2010 or newer)

For details about your Mac model, click the Apple  icon at the top left of your screen and choose About This Mac.

✅ - Download the macOS 10.13 High Sierra upgrade installer here:

https://itunes.apple.com/app/macos-high-sierra/id1246284741?mt=12

(Don’t use FireFox for this link)

The download will place the "Install macOS High Sierra" application in the Applications folder. Double-click the installer to begin the upgrade process. 

No one from Apple is here just users like yourself.

The App Store Updates page only informs you of updates available for the OS you are running.

Installing a newer OS is called an upgrade.

Which OS you can upgrade to will be governed by which model and year your mac is.

Click on the  top left of your screen click on About This Mac to find out the year of your mac.

For older OS’s,

Open Safari and click on this link, 

How to get old versions of macOS – Apple Support

Go to Check Compatibility to see if your mac qualifies for the OS upgrade you want.

Then go to the Download OS section and click on the OS you want to install.

Before upgrading make a full back up of your Mac.

Check that third party apps you use have updates available for the new OS.

https://roaringapps.com

Check that your printers/ scanners etc have updated drivers and software available for the new OS.

Connect your mac to your router via cable rather than rely on WiFi.

Do not use your mac while it is downloading

and do not use any other devices that share the same internet connection.

If the App Store says ‘Open’ then it is detecting a previous download of the install app

go to the Applications folder locate Install macOS ******.app.

Move it to the Trash, empty the Trash.

Restart, click on the link again, the App Store should say ‘Get' or 'Download'.

If you want to or are able to install Big Sur, open Safari and click on the link below.

How to upgrade to macOS Big Sur - Apple Support

If you are considering upgrading to Catalina or Big Sur be warned they do not support 32bit apps.

Your Mac is probably running 32bit apps and these will need to be updated to 64bit apps,

some updates may be free, some may be paid. Use this app to discover which apps you have

are 32bit, https://www.stclairsoft.com/Go64/ then contact the developers of the software to see

if they are offering 64bit updates.

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. Make sure to use Only Safari to commence the download as Other may not work

Make a Time Machine Backup Before attempting. Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina and Big Sur Only support 64 bit and there is no workaround.

Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs 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.

Update macOS on Mac – Apple Support

Please don't write in all caps.

You failed to mention a very important detail: what is the exact model of your mac?

Go to the Apple menu, select About this Mac, and tell us what is says, including the year - for example, it may say

iMac (21", late 2011) or iMac (27", early 2105). If your mac is too old it may not be able to run Big Sur.