I found this link on stackoverflow (https://www.dropboxforum.com/t5/API-support/999-quot-cancelled-quot-Error/td-p/192322) that is supposed to answer a question I have, but when I click on it, I get an error that says, "You do not have sufficient privileges for this resource or its parent to perform this action." It should answer my question here: https://www.dropboxforum.com/t5/API-Support-Feedback/files-listFolder-error-code-999-cancelled/td-p/288487.