Pages:"The file doesn't exist"

I was reading the books I had written on pages for fun and I tried to open one of them but it didn't let me. It popped up with the error "The file doesn't exist" and it took me ages to write that file. I tried to do whatever I could to fix it but unfortunately nothing worked. I have all my apps updated and nothing is old, so it is something to do with pages itself.

Please let me know how you can help,

Veerica