Can't download Sierra from the App Store.

I'm running 10.10.5 I'm need to upgrade to Sierra to run the newer Xcode. I'm trying to make a bootable USB install disk using this: https://www.macworld.com/article/3092900/macs/how-to-create-a-bootable-macos-sierra-installer-drive.html I get to the app store and it says "we could not complete your purchase. This version of macOS 10.12.6 cannot be installed on this computer" The instructions say to click "download" but I don't see "download" so I click "get" and this is when the message comes up. My last Hackintosh upgrade was done by allowing it to upgrade and not going thru the regular Hackintosh way. Q. How can I upgrade if I can't get OSX to install on a USB? I just need to find the place to download. Can I also just upgrade direct thru the "your computer needs updates?" Q. is there some where else I can get the download from? Why would it say I can't install it and why is there no download?