The handler name should match exactly

Author: kushaldas

install_files/ansible-base/roles/ossec/handlers/main.yml

@@ -1,6 +1,6 @@
 ---
 # Single handler to operate on *both* OSSEC hosts, server & client.
-- name: Restart ossec service
+- name: restart ossec
   systemd:
     name: ossec
     state: restarted