Well, after trying everything, and asking everywhere, I ended up getting answers in the Google forum itself, in the American forum, an expert told me that the problem was because my blog was testing, and I did not have much traffic , posts and stuff like that ... So no results came out. According to him, as long as I was using it, it would work.
And in the Brazilian Google forum, I find out that this is happening to many people, it's a blogger problem and they've been trying to fix it for a long time. And apparently, it's not an easy problem.
So the solution would be to use other types of search boxes, which although they are not the same as the blogger, at least they work ...
Here's one I'm using on my blog (since they do not all work).
<style type="text/css">
#pesquisafsm-caixa {
background: #eee; padding:10px; border:0 none; width:170px;
}
#pesquisafsm-botao {
border: 1px solid #222;
color: #eee;
background: url(http://i.imgur.com/cz4sguf.png) no-repeat left #4591fa;
margin-left: -3px;
color:#fff;
font: 'trebuchet ms', trebuchet;
padding:10px 10px 10px 22px;
border:0 none;
font-weight:bold;
border-top-right-radius: 7px;
border-bottom-right-radius: 7px;
}
#pesquisafsm-botao:hover {
cursor: pointer;
background: url(http://i.imgur.com/cz4sguf.png) no-repeat left #2375E6;
}
</style>
<form action="/search" id="searchthis" method="get" style="display: inline;">
<input id="pesquisafsm-caixa" name="q" placeholder="O que está procurando?" size="40" type="text" />
<input id="pesquisafsm-botao" type="submit" value="Pesquisar" /> </form>
Search box tutorial: link
