What is the meaning of posting a position-opening announcement multiple times at a research-focused institution?
I don't know what kind of position it is, but are you sure it's not additional instances of the position being offered?

That said, it sounds as if they're not getting the applicant pool or number of applicants that they want.  In my experience, hiring committees want three or four good candidates, even if one stands out from the rest.

Maybe they have found that your qualifications don't meet the requirements as well as you think they do?  Your not getting an email back from the search committee chair is probably significant -- or maybe your email got lost in the internets.