If your applicants are unable to upload a file that is a supported file type for your form, have them do the following:
1. From their computer, right-click the file > Select 'Properties'
2. Have them check the type of file > It is highly possible that the filename may contain ".doc" or something similar, but it may be a different type of file altogether
3. Have the applicant be sure they are not using a third-party conversion tool as this may corrupt the file - the file should be made with its native program (e.g. Microsoft Word for .doc files, Microsoft Excel for .xlsx files, Adobe for .pdf files)