USPostal service letters (remember them?), email, phone calls/tree, cell phone texts, Knock on door leave card in door..... You try, you "do your best".
When you are convinced the horse is dead, you quit beating it. Schedule a last B&G picnic with magician and catered BBQ, spend the last of the Pack's treasury, transfer the remainder on to the CO, and move on to ScoutsBSA.