I am posting a solution for the frequent error of the PayPal 3.x module for Prestashop of the type :

Veuillez contacter le marchant:
1. PayPal response:
2. SILOVER -> name=SANDBOX3.API.1&silo_version=880&app=slingshotapi&TIME=244402772; domain
3. TIMESTAMP -> 2014-10-24T17:49:03Z

You just need to modify the file modules/paypal/api/paypal_connect.php.

Replace:

if (!$simple_mode || !preg_match('/[A-Z]+=/', $tmp, $result))

With this:

if (!$simple_mode || !preg_match('/[TOKEN]+=/', $tmp, $result))

Good luck!