TOPIC: unable to add xls(x) attachment to e-mail from mail attendees screen

I.m trying to send an E-mail to attendees from a certain event, but only able to select images from selection panel. Although the xls(x) files are being present in the directory, Dt register doesn't show them for selection. already updated the Mime types etc, but no result.... Am I doing something wrong? if so, please give me some directions to be able to select files like WOrd, PDf and Excel.