Cannot find High Sierra Anywhere
I followed the instructions at https://support.apple.com/en-us/HT208969 and it opened my App Store, but High Sierra doesn't come up to download, just the App Store Main Screen. I am currently running Sierra on a MacBook Pro Early 2011 (Model: A1278). I should be able to update to High Sierra, which is the latest supported version for my mac, but I can't find it anywhere. Any help is appreciated. Thank you.
MacBook Pro 13″, macOS 10.12