Yesterday I found out that one of my H2 EU switches is unresponsive. I tried to restart my M3 hub several times, but with no luck. So I decided to reset the switch and pair it again. In every manual I found, it was written that I have to press 10 times any button. Well, this works apparently only if you have neutral wire connected.
So, if you’d like to reset your switch without neutral wire, you have to switch on and off the circuit breaker 10 times. At least, it helped me.