Yealink C920 password issue

[DaveK]

Hi,
I have been given a CP920 conference phone by a friend who no longer needs it. I am trying to do a factory reset so that I can use it. The issue is when I go into the Advanced menu it asks for a password and the default "admin" does not work. When I asked my friend, he said they never set a password.

Is there a way to do a factory reset without knowing the password? Or is the phone bricked and useless?

Many thanks for any help that you can give.

Dave