I'm not familiar with that library but should you "await" the handshake first before sending the message?
In any case if we assume the broadcast was successful (you can use
WireShark to monitor your network and see the bitcoin messages sent to make sure), the reason why your tx doesn't appear in any explorer could be the transaction itself. It could be invalid (wrong signature, already spent inputs, etc.) non-standard or simply paying a low fee that led to the rejection of it by the other node.