The message code of A9 means " MESG_SEARIL_ERROR_ID".
Could you please check if your command have anyone of following problems:
1. The network key was not correct?
2. The check sum of the command was not correct?
3. The size of the command message was too large?
The summary of ANT message code can be find in page 84 of the document of "ANT Message Protocol and Usage".