Hi @JosiasNavarro ,
Thank you for posting on the Instructure Community!
There are a few possible reasons for this behavior in my experience:
1) Canvas attempts to submit a file that is an unsupported file type.
2) The internet connection is unstable, and Canvas is unable to complete the file submission.
3) The file is corrupted.
Of course, I feel reaching out to Canvas support is the best thing to do. In the meantime, you can try clearing your cache from your browser to see if that helps. I also know using other internet browsers can help too (example: using microsoft edge instead of chrome).
All the best to you!
Noah