[Plugin: Alkivia SidePosts] Stylesheet ist listed as inactive

Hi,
i am wondering why my stylesheet ist listed as inactive. I think because of this i can’t remove the date whith such comment

#sidebar span.sideposts_date {
display: none;
color: #474747;
font-size: 10px;
font-weight: normal;
text-decoration: none;
}

right?
Can anybody help please?

I have already tried all the other advices here. But no one worked for me.

Thanx in advance!