updating from OS X to Catalina not working

Hi,

Downloading Catalina using Safari on your Mac.

How to get old versions of macOS - Apple Support

arakalle wrote:

i recently had a new hard drive put in and operating system has been put as OS x. Now I try to update operating system to a newer one and the app store says I can't

How to reinstall macOS from macOS Recovery - https://support.apple.com/en-us/HT204904