Hello,
Need to ask a couple questions, I’m not sure about your configuration but this could be a connection issue or even a configuration issue.
Basic troubleshooting:
- Firewall
- Selinux
- systemctl status graylog-server
- systemctl status elasticsearch
- systemctl status mongod
- curl -X GET http://localahost:9200/_cluster/health?pretty
- journalctl -xe
I found this, It may help
And this