Attachements cannot be aquired

We have created a form, where we allow users to upload word and PDF documents. Usually, they should be stores so that we can download and review them. However, for some reason it doesn’t work. WordPress created a link to the file, but whenever we click on the file to “collect” the document, there’s an error messagt reading “Ooops! Page not found”. When we try to export is as PDF and review it, there is no site to review it and even if we export the whole data in .csv, the link doesn’t work.

How can we fix this?