Taggin system not working

Hi i'm workin in a new site http://s364105922.mialojamiento.es/tuducha and the k2 taggin system is not working. I write the tag and the coma or enter and the tag doesn't change to green, and when I click the save button the tag disappears.
Can someone tell me how to solve this?

Thanks and excuse my english

PD: I have tried to change the k2.css with the k2.css default file because I had read in k2 forum that this could be the problem, but the tag system doesn't work anyway

I have the exact same problem.