Is it permissible to strive to mend the relationship between a couple after the third divorce, and would such an endeavor be considered a sin in this case?

If a man divorces his wife thrice, she becomes irrevocably separated from him (baynunah kubra), and she is not lawful for him again unless she marries another man willingly and he consummates the marriage with her, and then he separates from her either by divorce or death, and her 'iddah (definition) (waiting period) from him ends. The return of a thrice-divorced woman to her former husband without another marriage is forbidden and a grave sin (kabirah), and assisting in it is not permissible. However, if the husband is not certain about the occurrence of the three divorces, he should consult a Sharia (definition) court or trustworthy scholars, and if they rule that the three divorces did not occur and that reconciliation is permissible, he should act according to their ruling.