Paypal sandbox: not enough money on mobile

[elvizgz]

I'm working on a webpage made with Prestashop 1.5.5.0. I've configured PayPal module and I'm processing payments with sandbox account correctly.

 

Now I'm testing the website in my mobile but when I try to make a Paypal Payment, I get the following message after login my PayPal facilitator's account:

 

"We're sorry but your PayPal balance and payment methods aren't enough to finnish this transaction. Associate a credir card" (this is not the exact message. I made a translation).

 

I don't know why I'm getting this error just in the mobile. In my PC it works fine. The webpage it's a responsive one so the code it's the same.

 

Any ideas why I'm getting this error?

 

Thanks in advance.