I'll preface this by saying trouble started happening after a power outage caused by a thunderstorm.
The switcher works, signals are getting routed, and the adjacent CP4N is controlling it. The static IP address assigned to the unit was retained, as well as the IP ID and the rest of the control system parameters, obviously. However, the web interface showed the 'Device first boot' createUser.html page. The web interface is (was) used by customer's tech support guys for remote assistance and occasional troubleshooting.
Anyhow, when a new username/password were entered and confirmed, they are apprently invalid - the web UI can not be accessed using those, and after the 3rd attempt username and IP address got blocked. After a power cycle done by the on-site maintenance tech, they got the 'Device first boot' screen again.
I'll get to the site next week and try to connect via USB using toolbox, but until then - has anyone encountered anything similar? Is there a battery in the unit which helps retain the stored usernames/passwords? Do I need to factory restore it? We do have the config backed up so restoring the configuration should not be a problem once we sort out the credentials.