The first thing I would do is check to see what version of the
JSP and
servlet spec the new container supports and then make sure it matches the version of Tomcat you're using.
The latest versions of Tomcat tend to way ahead of most commercial containers when it comes to supporting the newer specs.
Also "..the application is not working." is a useless statement in a web forum. In order for anyone here to help you, you need to be able to tell us exactly what isn't working. Find out where the logs are in your container, figure out if and how the log levels can be increased to display the maximum amount of information, and then, if you don't understand what is in the logs, post the relevant sections so someone who might can take a look and possibly give you some advice.