The sound does not play during the playback of a video or audio file. November 25, 2020 05:52 Updated Open the Control panel and check that mute has not been selected. Related articles Can't hear the application's sound through the speakers. Can't play the video on the app. (Black screen) Content or a thumbnail is displayed in a color tone different from that of the original PDF (document), with a loss of an image, or as a blank page. 4.Using Content A content has been published, but the content does not appear on the "New Contents" on the app.