@Gioacchino
I understand what is problem but I need some extra data.
What kind of paypal payments you use, standard or digital?
- this can be set in plugin settings
Can you also set osp_debug to true in index.php in plugin? After each payment you should get email with data used
- means to change define('OSP_DEBUG', false); into define('OSP_DEBUG', true); and test next payment. Once done, you shoud get email with raw data regarding this payment.
- also check what is in comment in payment directly on paypal, it should have specific code
I've just updated plugin to 1.3.4 with some own experience and updates in paypal core, please check it (just replace theme files).