Can you be a bit more specific? Meaning, when you say it isn't picking up the tower, is it simply not going to cricket or do you not have any connection at all?
Check to make sure you are in a market that will accept a triband phone. Some Cricket markets are AWS.
Also, check to make sure you have the correct pairs. Everytime I flash a phone, I always set those as well to get them to go to the Cricket towers.