Hi,
I believe the relevant issue is "Closed" detection of a listing. Auctiva periodically updates their database with a sync against eBay, that cycle occuring about every 4 to 6 hours. However, I've seen cases reported and personally experienced longer delays in that update occuring. A Buy-It-Now is not a "scheduled event", like the normal end of auction-sytle listing. It's possible a scheduled event has better treatment, i.e. is anticipated by the system. Closure by update is a weakness in the Auto-Relist processing concept that may be unavoidable using the current methodolgy of update (if I'm even correct on how it works).
Question: Are you using eBay or Auctiva checkout? I'm asking because I don't know if the Checkout process would help Auctiva detect the closure/sale.
Danno