A pre-approval letter alone doesn't tell much- it's a starting point, not a guarantee. I am a licensed mortgage broker as well as a real estate broker, so when a buyer's financing comes across my desk, I verify it myself before you ever sign anything- not after you've already taken your house off the market and told your family it's old.
If you've got an offer in hand right now, upload the buyer's pre-approval letter below and I'll take a look personally.