Typically, I follow the rules of the auction host for such things.
Personally, about 10 business days with no communications is my Point of No Return.
Bad things happen to good people, and some leeway is warranted. Like, if I'd sold something to a person in Baton Rouge or Lake Charles, they would have only gotten power back last week. Now, that's worth some leniency. Or a car wreck that puts them in a hospital. Either of those are like to interrupt communications.
But, the waiting in silence is tough sledding. It's worse if the sold item shipped already.