client installed by clonezilla not inventoried

I have a classroom installed with one clonezilla image with windows 7 64bits, i have installed agent to inventory PCs, first of them works perfect, it's registered in server, but when i install agent in the second o third ... they don't appear in server. I have configured server with detect duplicates just by mac address.

Is there any problem with PCs with same license or OS id?

Thanks a lot,