Hello, the factory default procedure can be found in the User Guide or here: http://community.cambiumnetworks.com/t5/ePMP-Installation/How-can-I-reset-the-AP-or-SM-to-default-configuration/m-p/33684#M6
The default UN/PD should now be admin/admin. You can also try logging in using 169.254.1.1 address.
However, if you have the retain passwords feature enabled, you might be out of luck. A support case would be needed to see your options (probably reset via SNMP). http://community.cambiumnetworks.com/t5/ePMP-Configuration-Management/Retain-passwords-upon-factory-default-procedure/m-p/63478#M32
A last option would be to use the discovery tool to see if it can be located and accessed. https://support.cambiumnetworks.com/files/epmp/#r3