While doing an initial install of FreePBX, my IP phones’ admin password kept getting changed, and I could not find any help on the subject.
Finally re-visited the global setup options for Endpoint Manager (EPM) which I was using to configure the phones and realized there are two fields that allow EPM to change admin and user passwords on configuration. I tried the admin password on one of my Cisco phones and indeed that was the password to which it had been changed. Cockpit error on my part, but also a function of learning curve.
With so many details to discover when setting up a new system, a newbie like me can easily miss this. I hope this will stop a lot of head scratching.