One reason could be that your files do not have file extensions. On a Mac, file extensions are not necessary. However, on Microsoft-based operating systems file extensions are used to designate the type of file, which allow files to open in the correct programs. This is also how file types are determined on the Internet. If your filenames do not end with the appropriate file extension, this can cause problems with the conversion of your documents and ultimately with the viewing your manuscript proof. You should add file extensions to the end of the file name for all documents you upload to Paragon Plus Environment.