ENDIAN Firewall - Endian UTM mini is not responding

I am the user of an Endian UTM mini (still v2.4 I believe).
The system worked fine (was configured non-DHCP).
Yesterday we hav power failure and after that it seemed it stopped working.
I can not logon on the device (using the green/LAN poort).
Still the device behaves quite normally.
I have rebooted with power off/on.
At startup the disc-LED blinks, and after few seconds the activity-light starts blinking and the Ethernet-1 LED also blinks.
I believe this is normal behaviour.
I cannt ping the unit, but probably that is normal also.
I tried to do SSH-connection but that also fails (Network time-out).

The Console-port is nice but I dont have any RS232-device or converter.

So How can I test if my Endian died ?
And if he didnt die, how can I logon again (can I use reset-button to restore to factory defaults? ... manual mentions nothing about reset-button by the way)