Can't upgrade to Mac OS X High Sierra

I am on Sierra, version 10.12.6, and I'm trying to upgrade to High Sierra via the link here: https://apps.apple.com/us/app/macos-high-sierra/id1246284741?ls=1&mt=12. However, when it opens the itunes store shows this error:

To be safe I tried downloading Mojave from here: https://apps.apple.com/us/app/macos-mojave/id1398502828?ls=1&mt=12 and it gave me the same error. From my knowledge there are no other ways to download the updates from apple since they doesn't show up in the appstore either. I read on this forum (and tried their solutions) that this might mean that it's not available for me to download. Where can I download the High Sierra update?