I would expect a typically reputable seller to keep good contact, provide info about shipping costs and insurance and make sure that delivery is confirmed. At a minimum to reduce liability.
Failure to respond is indeed a red flag, and concern is warranted. I would recommend websearching the seller's name, phone number etc to see if anything is out there on him. Also full disclosure on this Forum could lead to additional information.
He has your money and thus a responsibility. Failure to keep contact should appropriately lead to action on your part.
Excuses are cheap and abundant these days.
Scorp