1. You are trying to upload a file that is not allowed by your instructor. (Ex: Trying to upload a .docx file when a .pdf is required.)
2. The dropbox file acceptance window has closed.
3. The filename of the document you are trying to upload has symbols (@#$%^&*><) in it.
Resolution
1. Recheck the instructions provided for uploading to the dropbox set by your professor to make sure you are submitting the correct file type.
2. Check the restriction dates on the dropbox to see if it is closed. Contact your professor to see if it can be reopened.
3. Rename the document on your device. While some punctuation is allowed, we recommend using only letters and numbers to name the file. Upload to the dropbox again.