Previous to version 188.8.131.52, the only file types supported by the Upload Batch Page were tif and pdf. Any other filetypes had to be imported via the email importer.
You can set this up by following the instructions in the following link:
Which files types can be uploaded via the Upload Batch page in the UI?
We support othe following file types: TIF, TIFF, PDF, ODT, ODS, ODP, ODF, SXW, BMP, JPEG, JPG, PNG, HTML, HTM, XLS, XLSX, PPT, PPTX, DOC, DOCX, RTF, TXT, PSD, ODG, SXI, SXC, SXD, WPD, LibreOffice Supported Types, Zip files containing compatible file types