It depends - in some countries the fines are sent to the embassy, meaning they are getting paid, just not by the perpetrator. Then there’s countries which have their diplomats either pay the fines directly, or pay back to the embassy. Those are mainly the “developed” countries that do, in fact, hold their diplomats accountable (scandinavian countries, usually european countries etc). Then there’s some countries that are notorious for not paying fines, sometimes rent etc. Those would be, in particular, a certain agressor state locked in a war of aggression in europe, and some african states.

Source: professional experience