If you think files are missing in your Canvas site, then a known Canvas bug might have affected you site’s folders, the ones used in the “Files” area of Canvas. Here’s the issue:
Folder names that have spaces at the end of them inconsistently display files.
“How Do Make the Files Display?”
There’s only one solution to this issue:
Re-name the folders and make sure there aren’t spaces at the end of the names.
“But How Do I Know This Bug Is Causing The Issue?”
If you don’t see a file and aren’t sure the issue is spaces in the folder name

Try adding a file to a module in your Canvas site.

If the test is inconclusive, please contact Courseware Support (canvas@pobox.upenn.edu) for assistance.
“Will This Bug Be Fixed?”
Canvas’s engineers are working on a solution to this issue. When this bug is fixed, it will be announced on the Canvas at Penn site. In the meantime, please use the information above if you’re experiencing this issue. If you have any questions, please email Courseware Support (canvas@pobox.upenn.edu)
Update: Bug Has Been Fixed!
Canvas’s engineers have deployed a fix to this issue. If you have any questions, please email Courseware Support (canvas@pobox.upenn.edu)
Last Updated: 24 Jan 2019