Field refused by the declared exchange profile
The payload contains a field the declared exchange documents as invalid on that endpoint.
What it means
Prebid Server returns 400 on requests that define wseat or bseat. Bidder selection is imp.ext.prebid.bidder.{bidder} (or legacy imp.ext.{bidder}), not the OpenRTB seat allow/block lists.
Why it matters
PBS treats seat lists as an OpenRTB difference, not a filter. Sending them is a protocol error on /openrtb2/auction.
How to fix it
Remove wseat and bseat. Name bidders on each Imp. Or drop --profile prebid-server if you meant a different exchange.
Example that trips it
{ "id": "req-1", "wseat": ["appnexus"], "imp": [{ "id": "1", "banner": { "w": 300, "h": 250 }, "ext": { "prebid": { "bidder": { "appnexus": {} } } } }] }Validated with --profile prebid-server. wseat is legal OpenRTB and illegal on PBS.
Check your payload
Paste a bid request or response into the tester to see whether this code fires against it, or gate on the id in CI with the CLI: the id is stable, wording is not.
Back to the full diagnostic code reference.