Here are some possible reasons:

  • Campusnet has a file limit size of 5MB per each upload. If you are trying to upload a document that is larger than 5MB, you will need to edit the document, or contact your professor to determine what he/she would have you do.
  • The time for uploading has past. Contact your professor to determine what he/she would have you do.
  • There is only one upload allowed for that specific assignment. Contact your professor to determine what he/she would have you do.