When I click it I get a 404 Not Found page (with the awesome mole graphic). Another curator of this project confirmed the same problem. It was working yesterday.
As a work-around (for any other project curators who use this tool), you can use the Identify tool with this search URL (you’ll have to specify the project in the filter):
Sorry, I removed that ancient page and didn’t update that link to the current version of obs search. Will try and get that fixed and released before the end of the day.