migrate sites to an other server fails

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Reason: SOAP-ERROR: Parsing WSDL: Couldn't load from 'https://<ip>:2083/apnscp.wsdl' : failed to load external entity "https://<ip>:2083/apnscp.wsdl"

         0. SoapClient->__construct("https://<ip>:2083/apnscp.wsdl", [connection_timeout:30, location:"https://<ip>:2083/soap?authkey=7ac1cd0a07363efdf5fe3ef1cefde99c84fb5a42af7de20b4f18d8110fb91203", uri:"urn:net.apnscp.api", trace:true, stream_context:stream-context])
            [/usr/local/apnscp/lib/Util/API.php:71]
         1. Util_API::create_client("x", "192.168.11.112:2083")
            [/usr/local/apnscp/lib/CLI/Transfer.php:545]
         2. CLI_Transfer->_api_key_valid()
            [/usr/local/apnscp/lib/CLI/Transfer.php:515]
         3. CLI_Transfer->_create_api_client()
            [/usr/local/apnscp/lib/CLI/Transfer.php:147]
         4. CLI_Transfer->process()
            [/usr/local/apnscp/bin/scripts/transfersite.php:233]


array (
  0 =>
  array (
    'message' => 'Setting migration stage `1\'',
    'severity' => 1,
    'caller' => 'unknown',
    'bt' => NULL,
  ),
  1 =>
  array (
    'message' => 'Setting server `192.168.11.112\'',
    'severity' => 1,
    'caller' => 'unknown',
    'bt' => NULL,
  ),
  2 =>
  array (
    'message' => 'beginning migration: <domainname> (stage 1)',
    'severity' => 1,
    'caller' => 'CLI_Transfer::log',
    'bt' => NULL,
  ),
)