No voltage and frequency on phase A and B

I have two Shelly Pro 3 EM devices that are showing the same error. This is the one connected to the inbound wires to the apartment, but my second one connected to the stove, shows a similar story.

As shown above Phase A and Phase B doesn't show neither Voltage nor Frequency. I read in the manual about the "phase sequence" error, and today the electrician was here to measure that the correct sequence of phases are connected to the appropriate terminals. Neither me, nor the electrician could figure out the problem. Anyone has any ideas?

After some further investigation about this I realise that the device power supply might be connected to phase A instead of phase C, as indicated in the wireing diagram. Could this maybe be the cause of my problems?

Zitat von thgoebel

A Shelly pro 3EM gets its power via terminal C. Terminals A and B are used to measure the voltage between A and N and B and N. Terminal C has a measurement equipment too.

Thus, you‘ll have to check whether you need three channels. If you need one channel only, this should be channel C. But two or three channels should be wired correctly.

Obviously, terminals A and B are not properly wired with the two live wires.

Thank you. I will ask the electrician to try that.