Hello.
This error message is shown when Filebeat does not push the index template to the Indexer node. Could you check that Filebeat is working properly? Please run the command: filebeat test output.
I also recommend you check the documentation on this point. You should not receive this error if you have followed all the steps correctly. It is important that you insert the new template into the Wazuh indexer, using: curl -XPUT -k -u <INDEXER_USERNAME>:<INDEXER_PASSWORD> 'https://<INDEXER_IP_ADDRESS>:9200/_template/wazuh' -H 'Content-Type: application/json' -d @template.json.
Remember to restart Filebeat and the Wazuh server components.
If that still causes an error, please check the wazuh indexer service status using: systemctl status wazuh-indexer. Also, you can share the /var/log/wazuh-indexer/wazuh-cluster.log file.
I hope this will be helpful.