My rear fog ligt does not work any more. The main switch is okay, the fuses is okay, this "plates" in the lamp is okay all way to the connecting point, and the grounding is okay. I think there is a problem with the wire between the rear lamp connection, and the fuses. Any relay on the rear fog lamp?

Any suggestion where to start looking for breakage at the wire?

Are you sure they have ever worked? I'm under the impression that some cars does not have working rear fog lamps, I think I read it in a post here somehwere.
I have the same issue on my Roomster, everything should be working but doesn't.

You have to go a long way back before Skoda Roomsters to find a car in Europe / EU that does not require at least one rear fog light for Type Approval / C&U.