Error 20135: Best offer feature is unavailable or disabled for the specified category or listing type.

This message will be returned if the listing category does not support Best Offer, or if the Best Offer feature has been disabled on an auction listing that has received one or more qualifying bids. In these scenarios, the BestOfferEnabled, BestOfferAutoAcceptPrice, or MinimumBestOfferPrice fields will have no effect if included.