Keepon,
The same sort of thing happened to me also. Bought an item w/ quantity listed a 2 left, but by the time I used BIN, the seller was out. They refunded and we left FB for each other. We also filed for a mutual cancellation. A few days later I received the same warning. It kept showing up for 60 days then went away.
A seller cannot see the alert, when checking FB. Even UPIs do not show up. Just bear with, and it will go away.
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THE BEATINGS WILL CONTINUE, UNTIL SELLER MORAL IMPROVES