Please note that the <account-access-key> should be set to the access key found in your license:
If the settings are all correct, the next thing to verify would be connectivity from the server with the machine agent to the controller. You can test this by either opening the controller in a browser from the machine agent's server, or with the following command: telnet <controller_url> <port> (This is only for testing connectivity so if you connect successfully please exit telnet with Ctrl-C)
Also, if there are any other messages in the log, particularly ones marked as ERROR, that could provide more clues. On the other hand, if for example you simply have the server name wrong, then the log will only show that same message repeated every minute.