Invitee can add photos to album, but I cannot see them?

I have successfully shared an album in Lightroom CC with my colleague with "edit and contribute" permissions. I can confirm that we both can see the photos I have included in the shared album. However, when my colleague adds his own photos to the shared album, it does not show up in the album for me and cannot view any of his photos.

Can someone please assist? Not sure if I need to enable something or if I have shared it incorrectly. Currently using the most updated Lightroom CC Desktop app (Windows for myself, colleague uses Mac).