First, please make sure that you are attempting to upload one of the supported file types (see What file types or formats can I upload?). If your file is supported, please try again using a different browser (e.g., Firefox or Chrome instead of Safari). This should resolve the issue in most cases. If you continue having problems, you may need to try using a different computer or network (such as at home instead of school). If the previous troubleshooting suggestions didn't work, it's possible that your file may be corrupt. In this case, you can try recreating the file, saving the new one, and attempting to upload it.
Please also watch our QuestTips video for some helpful tips on uploading materials.