This is a simple product, not the best I saw. When I pushed to the mains, nothing happened. I had to read the manual, it is battery operated ( not incl.), need to insert 2xAAA. After load with battery, push to the mains socket it displayed: the wiring is INCORRECT. OK, have to change the Live and the Neutral. Reverse the unit to change the terminals. It shows the CORRECT info, meanwhile indicating the right terminal as Live. Remove the unit and test the right terminal, it was the Neutral.
After several check procedure, I found the terminals were reverse soldered to the circuit panel inside. After I changed the red and black wires, the live terminal indication get correct. I recommend to test manually.
There was a bigger problem, when pushed the RCD test button. The whole house electricity went out. This button simulate the >30mA current leakage through the Earth wire. My security relay has been triggered immediately. Unfortunately, the RCD test button is easy to push unintentionally and easy to make electricity interrupt. As a prevention, I moved more deep the button inside the case by 2mm, to avoid such unintentional failure in the future.

Good Quality and Fault Identification. Overall Satisfied.