Yahoo has discontinued the BOSS V1 API. For the BOSS V2 api, they have moved to a paid subscription model.
We discontinued the BOSS Search extension because of this and have replaced it with the Bing Search extension.
However, we received word last week that Bing will also be moving to a paid subscription modal, and discontinuing the current API.
We are currently in the process of evaluating the search services to find a new free service to work with.