message: photo sharing not available for this device

I received an email invitation to a shared album and when I clicked on the Subscribe button I got the message "photo sharing not available for this device". I checked my system configuration and it is definitely set up to share photos via iCloud. I looked for help on the web and the closest answer I got was: Some Mac users may find that when want to join a new shared photo album, they are required to click a "Subscribe" button in the notification email and navigated to the Safari web browser but find "iCloud Photo Sharing is not available for this device". At this time, you can remove the subscriber and then re-add the albums to share again.

Not exactly helpful. How do I remove the subscriber? How do I re-add an album that i never had access to? Help!

BTW, i'm using OS 10.13.3 and I checked that I am connected to iCloud (I can see it and access it in finder, and I logged into it via safari as well).