Update problem for Add-ons

The problems happen with these 2 plugins:
Newsletter – Add-ons Manager
Newsletter – WP Users Integration

Hi,
I have the free version.

@webagile

I have setup this code:

if(empty($_GET['action']) && $_GET['action'] !== 'test_curl')
	return;

$curl = curl_init();
curl_setopt_array($curl, array(
	CURLOPT_RETURNTRANSFER => 1,
	CURLOPT_FOLLOWLOCATION => 1,
	CURLOPT_URL => 'http://www.thenewsletterplugin.com',
	CURLOPT_USERAGENT => 'Mozilla/5.0 (X11; Linux x86_64; rv:61.0) Gecko/20100101 Firefox/61.0 cURL test request/1.0'
));
// Send the request & save response to $resp
$resp = curl_exec($curl);

echo 'Status code: ',curl_getinfo($curl, CURLINFO_HTTP_CODE);
  
// Close request to clear up some resources
curl_close($curl);

if($resp === false)
	die("Error");

echo $resp;

die();

You can see it live here: https://www.consultingroupitaly.com/?action=test_curl