When a TeamRaiser is set to "Accepting Registrations Only", the participant search function will no longer allow searching for participants in that TeamRaiser event.  You will need to change the event status to "Accepting Registrations and Gifts" in order to search for participants and teams.

In this case, the search is defaulting to the first available TeamRaiser event and searching through that. Normally, the default TeamRaiser pages will remove links to the Participant Search when the status is set to "Accepting Registrations Only", but this can be overridden if your pages are customized.  You can also confirm this by going to the Advanced Search function to see if this event is listed among the available TeamRaisers to search.

Please refer to this solution (BB746991) for more reasons why TeamRaiser participant search results are not populating as expected.