Hello Omar, thanks for your question!
Regarding the issue you faced with your C40 after a blackout, first thing we'd require is physical access to the codec. Do we have all LEDs on normally? Is there any issue with the LEDs?
Also, do we have console access to the device? Is there any output from there?
First thing we'd need to verify regarding this issue is if the hardware wasn't affected at all during the blackout.After that, we can move forward and review configuration / call flow / remote management.
Regards,
Victor