Electron E270 no connecting

One of our Electron E270 suddenly is not able to establish a cell connection.
Device doctor did not help to bring it back online, I assumed a problem with the SIM, which we've had in the past with other Electron's, but Particle-identify shows IMEI & ICCID, so it must be something else.
I've de- and reactivated the SIM as I've read in one post it solved a similar problem, but with no success.

The log file is available here

I don't think the community will be able to offer much help, since it seems to be either a hardware or backend problem, so I'd like to ask @support to take a look at it, thanks.

Thanks for the log. Your cellular connectivity and SIM are fine.

The problem is that the device keys on the device no longer match the cloud. I suspected this because the log indicated that the public server address was blank (Public Server Address was blank, restoring), typically indicating the configuration flash (DCT) was erased.

I verified this from the server side logs which indicate that verification of the DTLS session failed. That is caused by mismatched keys. Your device keys were most likely erased on the device and recreated, but the cloud does not know about the new keys yet.

The same incident that erased the server address probably erased the keys which are also in the DCT. This can happen on STM32 devices (including the Electron and E Series) in some unusual brownout situations.

It's not possible to repair the keys remotely, but you can do so using the Particle CLI with the device connected using USB using:

particle keys server
particle keys doctor
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Repairing the keys indeed fixed the problem, many thanks for the quick help!