Who sees them, and where they don't appear
OpenAI doesn't show ads on Plus, Pro or Business plans, or to users identified as under 18. Ads stay away from sensitive conversations and brand-unsafe contexts set out in OpenAI's ad policies, and qualifying advertisers can add negative phrases for their own brand rules.
What it means for advertisers
There is no search term report, so you can't see which conversations showed your sponsored result. Relevance matters as much as bid, and one answer carries one ad at most, so when a rival describes the same buyer better, they take the slot. That is why ads go missing and why it pays to check your buyers' prompts on a schedule.