going back to an old operating system

Hey there!

You can download older OS versions from here:

https://support.apple.com/en-us/HT211683

Although you do have to erase your hard drive to install them, and probably need to create a bootable installer with the old OS as well:

https://support.apple.com/en-us/HT201372

First will have to erase the internal drive (This is on Intel Macs):

https://support.apple.com/en-us/HT208496

Although if you’re Mac is a little bit older, you can startup with Shift Option Command R, erase the HD using Disk Utility, then install the original OS afterwards.

https://support.apple.com/en-us/HT204904

Another fact isn’t that if your Mac came stock with the newest OS, you will not be able to revert it to an earlier OS.

Hope something here helps, let me know!

Is this a New Issue ? If Yes, what exactly changed on this computer ?

Is this an Old Issue ? If Yes, what actions has the user taken to fix this issue ?

Details and context will really help to pinpoint possible solutions.