PHP - Plesk 12.5.x API no longer works on my site

Hello community,

a few weeks ago I succesfully create customer via PHP, but now will the API no longer works on my site.
The result is bool(false).

I hope you can help me and sorry for my bad english.

<?
#Plesk Country [start]
if($country == "Deutschland"){
$plesk_country = "DE";
}elseif($country == "Frankreich"){
$plesk_country = "FR";
}elseif($country == "Italien"){
$plesk_country = "IT";
}elseif($country == "Österreich"){
$plesk_country = "AT";...

PHP - Plesk 12.5.x API no longer works on my site