Problem installing High Sierra

I am currently still running macOS 10.9.2 and decided it was high time for an upgrade to High Sierra. Started installing it from the App Store, however realised it would take too long so cancelled the download with the intention of starting it again.

Now, however, the App Store icon says "Installed" rather than "Get" - even though it's definitely not installed? How can I restart the download?

Any help would be greatly appreciated!!