I can't find the New button to create a new Lead Assignment Rule
Sorry you're stuck but there's almost always a pretty easy fix! Do NOT try to start all over again, eg. uninstall Max's Pitch Package, etc. That can make things worse.
Before you post make sure you check the Help FAQ for an instant solution first. Then, if you can't find it there, you can post your problem here and we'll get to it ASAP (within 24 hours), but be sure you:
post in the right category
INCLUDE AT LEAST ONE SCREENCAP IN YOUR POST TO SHOW THE PROBLEM!!!!!!!!
explain the problem clearly