Does one need a heter to go to the secular courts if the beit din did not work or in place of the beit din?

ב"ה Shalom Yes, indeed .The Shulchan Aruch (חושן משפט סימן כו:ב) says that in a case in which one cannot save his money through a Rabbinical court or the party involved refuses to go to a Rabbinical court, one must ask the permission of the Rabbinical court to go the secular court to make his claim. All the best