My free iPhone Apple TV+ Sub not showing on web viewer

I got the free year subscription with my iPhone.

Its now extended up until Feb 2021 (which lets me view perfectly on iPad and iPhone), but when I try to view TV+ shows via the tv.apple.com website, it keeps asking me to subscribe to be able to view.

Why is the sub not showing there?

I just want to be able to watch on my desktop Windows PC.

Help?