Catalina updates

Forget trying to do it through System Preferences> Software Update.

First connect your mac to your router via cable instead of WiFi.

Next restart your mac, open Safari (do not use Firefox it will not work) and

click on this link,

How to upgrade to macOS Catalina – Apple Support

Go to Section 4 and click on Get macOS Catalina.

This will redirect you to the App Store Catalina download page.

It should say 'Get' or 'Download'

Do not use the mac or any other devices that share the same internet

connection while the mac is downloading.

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 Catalina.app.

Move it to the Trash, empty the Trash.

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

Can you not connect your macro your router via cable.

If your only option is WiFi then make sure that your mac is as close to the router as possible.

And do not use any other devices that share the same internet connection while the mac is downloading.

Catalina is an 8.24GB download so it will take a long time to download so perhaps enough time to redo

your kitchen.

What have you tried?

What error message do you get?

What did you download? You can not install an update before installing an upgrade.