A private marketplace (PMP) or programmatic guaranteed (PG) deal only transacts when several identifiers line up on both sides: the deal ID, the buyer seat, the currency, and, for private auctions, the flag that restricts the impression to deal bids only. If any of these differ between the SSP setup and the DSP's bid response, the exchange finds no eligible seatbid.
Common causes are a transposed or mistyped deal ID, a buyer seat that is not approved on the deal, a currency the exchange cannot compare against the floor, or a private-auction setting that excludes open-market bids the buyer is actually sending. Because the deal shows 'active,' teams often look at budgets first when the real problem is eligibility.
To diagnose it, pull a sampled bid response or no-bid reason with a timestamp and compare the exact deal ID and seat on both systems. The fix is to align the identifiers and currency, then request a test bid to confirm an eligible seatbid appears.