IONOS ftp-login via PHP not working but the connection via FTP client like filezilla works?

We receive the message on all possible systems where we have stored FTP login data (shopify, xentral etc.):

Upload failed: FTP Error: 530 Login incorrect.

The access data is correct because the connection via FTP client like filezilla works.

This Script:

$ftp = ftp_ssl_connect(FTP_HOST);
//$ftp = ftp_connect(FTP_HOST);

if (false === $ftp) {
    throw new Exception('Unable to connect');
}

$login_result = ftp_login($ftp, FTP_USER, FTP_PASS);

if (true === $login_result) {
    echo "login ok<br>";
} else {
    throw new Exception('Unable to log in ' . __LINE__);
}

$cd = ftp_pwd($ftp);

echo $cd . "<br>";

ftp_close($ftp);

works well with all ftp access data from various test servers except IONOS access data.

the very poor IONOS support (call center) can do nothing.

Is anyone aware of anything that IONOS has changed?