I save a lot of documents in cloud just for the purpose of me being able to check them with whatever device I am using. Recently, I tried to check a document that I have saved last July only to find out ALL of them are gone. I haven't deleted anything since the start. This is just so frustrating.
The Document Cloud files that you have been trying to access, is through the Adobe Reader desktop application. I would like you to check via https://cloud.acrobat.com/recent and see whether you have your document cloud files accessible from there or not?
If you see the files under Document Cloud storage on web (as shown in picture below)-
Then you may perform the following steps with the desktop app Adobe Reader DC-
1- Sign Out from the app and Sign In back.
2- Reboot the application as well as computer.
3- Check the update Open Reader>Help>Check for update