Problem with fulfillments

[AlessandroGnola]

I have a problem with send the fulfillments information.

In a previous store i used

echo $inv_url = 'https://xxxxxxxxxxx/admin/orders/{order_number}/fulfillments.json';


$inv_curl = curl_init($inv_url);
echo curl_setopt($inv_curl, CURLOPT_CUSTOMREQUEST, "POST");
echo curl_setopt($inv_curl, CURLOPT_POSTFIELDS, http_build_query($inv_data));
echo curl_setopt($inv_curl, CURLOPT_RETURNTRANSFER, 1);
echo $inv_result = curl_exec ($inv_curl);      
curl_close($inv_curl);

This function has alwais worked.

In the last store the result curl_exec  is blank.

I already checked the permssions. It's correct.

Why? How i can to check.

Alessandro