I have a mid-2011 Mac Mini running MacOS 10.7.5 Lion. According to everything I have studied and read, this Mac will run MacOS 10.13.6 High Sierra. However, MacOS 10.13.6 High Sierra can only be upgraded from MacOS 10.8 Mountain Lion or later. Accordingly, I have been attempting to download MacOS 10.8 Mountain Lion which is available to my MacBook Pro at the Apple site https://support.apple.com/kb/DL2076?locale=en_US, which clearly shows the icon of a Mountain Lion and a "Download" button. However, when this same site is accessed via my Mac Mini both the icon and the download button are not there. How can I download MacOS 10.8 Mountain Lion to my Mac Mini if I cannot select download at this Apple site?