Check in this order.
Are they in the database at all? Open the All candidates tab and search the name or email. Not there: they haven't synced from Bullhorn yet (new records take a few minutes; a large initial sync takes longer) or they are outside the synced scope. Contact support if it has been more than an hour.
Did a filter remove them? In AI Search, untick every required skill and clear excluded skills, widen experience to 0–30+, remove locations and Bullhorn filters. Re-run. If they appear now, add filters back one at a time to find the one that cut them.
Are they hidden? If you or a colleague hid them from this search, they won't show in this search. Start a New Search.
Is the resume parsed? Open their profile from All candidates. If skills and history are empty or thin, the resume in Bullhorn is missing, a scan, or in a format that didn't parse. Re-upload a text-based resume in Bullhorn; it re-syncs within minutes.
Wrong or missing location. If your search has a radius and their Bullhorn address is empty or misspelled, distance matching fails. Fix the address in Bullhorn or remove the location filter.
Language. Resumes in other languages are searchable, but if a required skill uses a term with no synonym mapping yet, tell support the example so it gets added.
Still missing
Send support the candidate's Bullhorn ID and the Search URL.