One heir lives abroad and is hard to reach. How can the estate matters go ahead?

The estate matters can go ahead, but that heir's share remains his right and cannot be ignored. Try to contact him through every channel available: close family, friends, his employer or social media. Keep proof of every effort. If he can be reached but cannot come home, he can appoint a representative through a power of attorney certified at an embassy or consulate. If he truly cannot be traced, inform the estate officer or the court, who will decide how his share is to be safeguarded. Never divide his share among the other heirs, even with the intention of making things easier. See cross-border matters.