I had an “Accepted Offer” but when I went to checkout the inventory was sold out. Why did this happen?

The expiration time for an Offer refers to how long the accepted price is valid and does not guarantee inventory availability.

If another buyer places an order for that inventory – either at List Price or their Accepted Offer Price – availability may be reduced or depleted.

Inventory is not secured until it is either placed On Hold, or is Checked Out and placed on an order.