Hidden Pictures/Videos not appearing in hidden album

Is there any reason why pictures/videos that I put in a hidden album are not showing up in the hidden album? Whenever I go to my "recents" album, all of the pictures/videos that I hid are greyed out and have a message that says "open hidden album to view media". Whenever I go to my hidden album, the pictures/videos are not there.

I should specify that the problem IS NOT that I cannot find the hidden album in photos. My problem is that my hidden pictures/videos are not appearing in my hidden album. I never deleted any of my hidden pictures/videos. This problem is happening across all of my apple devices (my iphone, macbook, and web browser version of icloud).