Error on activating plugin

I installed AliPlugin and when I use my key to activate i get this error which won't let me through. Any ideas?

Enter your License Key to activate the Plugin.

Warning: curl_error(): 437 is not a valid cURL handle resource in /membri/stronghands/wp-content/plugins/aliplugin/core/core.php on line 1144

Warning: curl_errno(): 437 is not a valid cURL handle resource in /membri/stronghands/wp-content/plugins/aliplugin/core/core.php on line 1144
failed: ()

Try to activate the server to server connections ("Setting"->"Server To Server").

Bye!