The cause of errors in the rendering process usually lies in an incorrect configuration of the applications (LMS, rendering service repository) with one another. For this reason, you must first ensure that all configurations were carried out as described.
Furthermore, false constants entered in the installation process could cause errors in the program flow. Constants can be corrected or adjusted at "[installation directory of rendering services] /conf/system.conf.php".
The rendering service provides a debug mode, which provides important notes for problem detection if it has been activated. The debug mode can be activated in the file "[installation directory of rendering services] /conf/system.conf.php" by setting "$ DEBUG" to "true". The debug messages are displayed directly in the browser.
Use the file "[installation directory of rendering services] / " to adjust the way the rendering service handles errors by means of the function.
For more information on possible errors see the log file of the rendering service, which can be located at "[installation directory of rendering services] / log / esrender.log". The log file of the Tomcat server of the edu-sharing installation can also be helpful.
If only certain file types cannot be rendered, this is probably due to a non-registered mime type or the lack of a correct MimeType-module mapping.
The error message "No rendering module found" clearly points in that direction.
If you experience problems when rendering audio or video files, the cause could be a malfunction of ffmpeg. Maybe the Linux kernel of your system is not compatible with the version of ffmpeg. Also make sure that the ffmpeg binary is executable by the webserver. References to other errors that occur in the conversion process, are also found in the log files at "[installation directory of rendering services] / log / conversion /".