Error Message: HTTP Status 500 – The server encountered an internal error that prevented it from fulfilling this request

The server installation is missing the Commons-Collections pack from the Tomcat installation. 

To solve it, you must download http://www.apache.org/dist/commons/collections/binaries/commons-collections-3.2.1-bin.zip and extract commons-collections-3.2.1.jar from it, then copy the jar file to the Tomcat/commons/lib directory ($TOMCAT_HOME/common/lib directory).