Tomcat servlet not running - error 404

Tomcat servlet not running - error 404

I have an application that is distributed with tomcat, I wanted to simply
take the webapp from the webapps folder and put it into the webapps folder
of a tomcat server, however when I do this and restart it etc whenever a
servlet is referenced (such as /controller) it returns a 404 as if the
servlets or the mapping aren't working. I'd provide more information but I
am so at a loss I don't even know where to start debugging this (very new
to tomcat) can someone point me in the right direction? Why would it work
locally but not on this server.