HOw do I upgrade my MacOS High Sierra 10.13.

Go to the App Store and search for ‘macOS’. You will want to download the most recent version (macOS Monterey) if your computer is compatible. Otherwise, see this article to get an older version of macOS.

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

I was having the same issue of the links not appearing from the page on how to uprade to older Mac OS versions.

I have a Macbook Pro non-retina 13-inch mid 2012 with High Sierra and 4 GB RAM. After I upgraded my RAM to 16 GB, all the links appeared. I'm in the process of downloading Mojave (for various reasons this is the OS I will use right now, one being that it is the last 32-bit OS). So *maybe* a memory upgrade to even 8 GB would help? I'm NO expert but I thought I would offer my experience.

Oh, and my computer is running a lot faster. I use Adobe Photoshop Elements and it is a big resource hog.

This post helped me: https://discussions.apple.com/thread/8588552?answerId=34037717022#34037717022

I was trying to upgrade high Sierra to Catalina or big Sur on my old MacBook Air mid 2013 11inch. All of the links to the older operating systems in that support article don't work now. a couple times when safari suceeded in connecting to the app store with the link, it says they do not exist on the App Store. Could there be some issue with my safari settings or something? Or has apple just made everything except Monterey unavailable? I am so puzzled.

HOw do

Apple's servers are having problems. :(