I've had to do a lot of reading to find answers to questions regarding passwords, default passwords, and forgotten passwords. If we had a master sticky of what to do for these issues for each model, that would be more useful.
What do I do if I don't know the password to a PxN client?
The master password for the P-Class is "Administrator". If you change the password and forget it, you will need to contact technical support and provide them with the "Challenge Code" from the locked device. To obtain the challenge code:
Options > Password >Reset and provide the Challenge code to technical support.