Xandr RTB error 5: Invalid Auction ID
What Xandr says
The auction id did not match.
Xandr reports this integer in the ${AUCTION_LOSS} macro on the bid's lurl. A search for Xandr RTB error 5 is this code.
What was checked
Xandr rejected the bid before price comparison. OpenRTB groups 1 through 10 as a response the exchange could not use: a bad id, missing markup, a missing price, or a domain it will not accept.
What to change
Echo the request id Xandr sent.
The same number in OpenRTB
OpenRTB loss reason 5 is Invalid Auction ID. Xandr publishes this integer with that meaning.