Do please answer each mail with "to all" option in order to let other users solve their issues with your case if possible.
Can you tell me if that agent is properly connected and enrolled to the manager (
here on how to check that and
here on how to verify that from the manager's side)?
can you increase verbosity from the agent (
this is what you should modify for windows in
/var/ossec/etc/internal_options.conf ) and restart it in order to get more detailed information on the error?
Let me know how that goes. Have a great day!