AdvAgg is making a "Connection error" with compass/css3

When I ran https://tools.pingdom.com/#!/brkeM9/https://www.licitacao.online I see an connection error pointing to an AdvAgg file:

https://www.licitacao.online/sites/licitacao.online/files/advagg_css/com…

How could I fix that? I think this kind of thing slows down site load.

Drupal core is v7.56

AdvAgg is v 7.x-2.28

I´m using theme: Pixture Reloaded v7.x-3.1

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/22/feed