It's up to you.
Personally, I would wait a few days and then message them again.
If hey don't respond to that second message, wait a few more days and then message saying you will cancel the sale and refund the buyer if the item is not collected by a certain date.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
