If you reset to the device to factory defaults, the administrator password changes to the device serial number for versions PL6 (XX.5X.XX) or later of the software.
Try the machine serial number. After that change it.
From 1st january 2020 all the machine in case of Factory reset or firmware upgrade will have the admin password the serial number.
I reset factory my Xerox... after the reset.. the default password does'nt work ??
I test 1111, admin, 11111, my old password... nothing...
Do you have a tricks ??