Can't connect to the Nintendo eShop

Hi!
I can use all the online features, and the 3ds have the last update. But when I try to access to the Nintendo eShop through my wi fi it returns me an error.
At the moment, it only connects using the public DNS that provides google.

(PD. In case of need more info: the security of my wi fi is WPA-PSK and is configured with everything on automatic).

Thanks in advantage.
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edit. Is very annoying use the public DNS because it goes too slow...