I found the issue when I tried to download one of the files, I got the error message ‘File not found or deleted from server’ even though the files were still there. So, on the Downloads tab, I created a test page and reattached the first file, then I was able to go to my original file and download it, but not the other three. I went back to the test page and reattached the second file, then I was able to go to my original second file and download it. I did the same thing for the other two files, and then they also downloaded. Now, after a few weeks, it stopped working again.
I will try that. Thank you!
Thanks for you help Steve. Yes, I am logging in as an administrator. I am fairly new to WP, but I believe that it must be a vanilla site because the company that I work for only has one website.