I have a Mid 2012 MBP i5/2.5/16gbram/480gb.ssd with 10.8. I ran into a problem and had to reformat the hd which had been running Catalina. I have installed mt. lion 10.8. I have gone to many websites and tried to install everything from 10.9 up and no luck.
What is the procedure to get my computer back to Catalina?
Sandy
Try this Apple Support page:
Download and install current or previous versions of the Mac operating system on compatible Mac computers.
support.apple.com
When you click on your macOS version link, it will launch the App Store app and open the download page for you. This will download the installer into your Applications folder so if you want to keep a copy for future use (I think you should), when the download finishes and starts macOS Installer, quit and make a
copy of the file to a separate folder. Afterwards you can double click the file in the Applications folder and the installation should proceed.
I suggest you make a backup first, two or more if possible, before starting the installation.