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.