the photos on my shared album went missing

The photos on my shared album went missing. All the people I shared albums with lost all the pictures they sent and the ones I sent. The names of the shared albums are still there, but the shared albums don’t have any content anymore, no pictures at all. Before, there were so many pictures there, but now it’s zero. Why did all my pictures suddenly disappear from my shared albums? How can I retrieve them? Please answer, because I have a lot of important pictures in my shared albums.