[Global Site Search] Global site search plugin

I installed Global Site Search plugin in my Multisite blogdigitale.com (it’s under construction) but
for example, if I search the phrase “commenti pubblici” in home page I get as result ANY post … instead on contrary, I’ve a post with this phrase in the following subdomain:
http://blogdigitale.com/buonimpresa/2013/09/01/commenti-pubblici/
Can you help me ?