I am trying to replace a 5330 IP phone on a 200 ICP and have gotten a L2 DL error with every replacement set that I have tried. I realize that it is a firmware problem in the phone but i cant figure out how to downgrade the software in the set so that it will connect to the system. I have upgraded the CX controller with the latest software and Mitel's knowledge center is not helpful with the 200 ICP line of products.