Fundraising plugin: Problem connecting to paypal gateway at checkout

Hi, when I click on the the pledge button I receive this message during the checkout process:

Your pledge of $25 is almost complete.

There was a problem connecting to PayPal. Please try again.

There was a problem connecting with the paypal gateway. (CODE) There was an error contacting PayPal's servers.

Can you help me figure this one out? I'm in sandbox mode using advanced payments. I already created the API credentials and updated the plugin settings to reflect that.