I don't know what to tell you. That error can only occur if the host & key do not match up. It's the equivalent of using zabbix_sender and seeing:
"response"=>"success", "info"=>"processed 0; Failed 1; Total 1; seconds spent: 0.000018"
(Okay, that's the ruby version, but it's very close). You sent one item, but it failed to be recognized by the Zabbix server.