I am using Azure Managed Prometheus to scrape the metrics for the nginx application in my AKS cluster. Below is the scrape config defined.

prometheusConfig:
  global:
    scrape_interval: 30s
    scrape_timeout: 10s
  scrapeConfig:
  - job_name: 'ingress-nginx-endpoints'
    kubernetes_sd_configs:
    - role: pod
      namespaces:
        names:
        - ingress-nginx
    relabel_configs:
    - source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_scrape]
      action: keep
      regex: true
    - source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_scheme]
      action: replace
      target_label: __scheme__
      regex: (https?)
    - source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_path]
      action: replace
      target_label: __metrics_path__
      regex: (.+)
    - source_labels: [__address__, __meta_kubernetes_pod_annotation_prometheus_io_port]
      action: replace
      target_label: __address__
      regex: ([^:]+)(?::d+)?;(d+)
      replacement: $1:$2
    - source_labels: [__meta_kubernetes_service_name]
      regex: prometheus-server
      action: drop
    - action: labelmap
      regex: __meta_kubernetes_pod_annotation_prometheus_io_param_(.+)
      replacement: __param_$1
    - action: labelmap
      regex: __meta_kubernetes_pod_label_(.+)
    - source_labels: [__meta_kubernetes_namespace]
      action: replace
      target_label: namespace
    - source_labels: [__meta_kubernetes_pod_name]
      action: replace
      target_label: pod
    - source_labels: [__meta_kubernetes_pod_phase]
      regex: Pending|Succeeded|Failed|Completed
      action: drop
    - source_labels: [__meta_kubernetes_pod_node_name]
      action: replace
      target_label: node

and I am trying to query the Prometheus continuosly with the query sum(rate(nginx_ingress_controller_requests{service="${appName}"}[2m]), but sometimes I am getting the below data instead of some information

{
    "status": "success",
    "data": {
        "resultType": "vector",
        "result": []
    }
}

Sometimes I do get the result. But I am worrying why it is not returning info continuously is not clear.

I tried reducing the scrape interval and increasing the scrape_timeout. But no luck. I want to understand the problem here clearly