Shared album not visible across devices

I started a shared album while logged in on my iPad and invited my wife. She can see it and add to it on her MacBook but not her iPhone. And I can only see it on my iPad, but not on my iPhone or iMac even though logged in to my Apple account on all three devices. It's been 24 hours since I created the album. Why wouldn't it show up on my other devices that have the same apple account and are running Photos?

Also of note, the icloud.com version of Photos has my albums but does not show any shared albums as differentiated from just "Albums". And the shared album I created in Photos yesterday on my iPad does not show up on icloud.com Photos either on my iMac nor on my iPad in a browser. How can these "Photos" be different? They synch my individual photos within minutes.

Thanks for any help.