Hi, thank you for your question at Q&A.
The 404 error most probably indicates that the application is getting requests. If request were not reaching the application through the reverse proxy/ingress a 50x response would be more likely in my opinion.
So the first place I would check is the logs for your app running in kubernetes. You can do this with kubectl
The syntax for getting logs from a container in a pod is:
kubectl logs <POD> -c <CONTAINER>