Unable to Upgrade System OS from Catalina to Sonoma (on iMac)

iBmoonie wrote:

I've been trying to update my iMac's OS from Catalina (Verson 10.15.7) to OS Sonoma with no success. According to material I've found online, my iMac (Retina 21.5" - 4K, 2019 model) should be able to upgrade to the Sonoma OS. When I try to update my software my "Software Update" window pops up and the spinning wheel next to "Checking for updates. . ." just continues to spin on and on and on to no end. Any ideas or suggestions for this problem?

There are factors:

Some which are beyond your control and those which are totally under your control

Like poor Wifi connection

Slow wifi connection

Software on the computer interfering with the download process including AntiVirus Software

Notation: Removal of the AV Software may increase the chances of the download to perform as expected.

Running behind a Commercial VPN which may increase Packet losses or corruption of the download 

Turn off any Third Party Two Way Firewall like like Lulu and Little Snitch and try again 

Best Results are via Ethernet Cable to Router

Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal 

Try Again using the Software Update Applet in System Preferences / Setting 

Worst case - Restart in Recovery Mode and choose Reinstall macOS. 

This in theory will pull the latest version of macOS this computer qualifies to run 

That iMac should be compatible both with Sonoma (14.*) and Sequoia (15.*).

You could try using the App Store. Search for "macOS Sonoma" or "macOS Sequoia"; or use the links in this Apple Support document: How to download and install macOS - Apple Support .

iBmoonie wrote:When I try to update my software my "Software Update" window pops up and the spinning wheel next to "Checking for updates. . ." just continues to spin on and on and on to no end. Any ideas or suggestions for this problem?

It happens some times.

Try using the App Store. Open the App Store app on your iMac, search on "Sonoma" and you should be able to download it from there.

If that doesn't work let us know.