Nginx-Ingress connection to service timed out. 504 Gateway Timeout returned

Question

I've been struggling to solve a problem for days. I have a bare metal cloud instance with MetalLB and Nginx-Ingress deployed.

• Kubernetes: 1.29.2
• MetalLB: 0.14.3
• Nginx-Ingress: 3.4.3
• Nginx in Docker image: 1.15-alpine
• CRI: containerd://1.6.28
• CNI: Calico 3.27.2

Behind the Ingress I have a Jenkins instance and everything works fine. Now I'm trying to deploy an Angular app and I have used the same Ingress configuration in order to deploy it. The angular app sits behind an Nginx and I keep getting 504 Gateway Time Out and I just cannot understand why.

Nginx-Ingress is in the "default" namespace, Jenkins in a "devops-tools" namespace and Angular service in "development" namespace.

Note I've also tried a configuration using HTTPS on 443 but it yielded the same results.

Note curl on the Service endpoint returns the index.html

adminFrontend.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: admin-fe
  namespace: development
spec:
  replicas: 1
  selector:
    matchLabels:
      app: admin-fe-server
  template:
    metadata:
      labels:
        app: admin-fe-server
    spec:
      imagePullSecrets: 
        - name: pull-secret-gcr
      containers:
        - name: admin-fe
          imagePullPolicy: Always
          image: myimage
          resources:
          ports:
            - containerPort: 80
          volumeMounts:
            - name: certs-volume
              mountPath: /opt/certs/
      volumes: 
        - name: certs-volume
          hostPath: 
            path: /opt/data/certs
            type: Directory
---
apiVersion: v1
kind: Service
metadata:
  name: admin-fe-service
  namespace: development
spec:
  type: ClusterIP
  selector:
    app: admin-fe-server
  ports:
    - name: http
      protocol: TCP
      port: 80
      targetPort: 80
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: admin-fe
  namespace: development
  annotations:
    nginx.ingress.kubernetes.io/proxy-body-size: 10m
    nginx.ingress.kubernetes.io/ssl-redirect: "false"
spec:
  ingressClassName: nginx
  tls: 
    - hosts:
      - subdomain.domain.com
      secretName: domain-tls-development
  rules:
    - host: subdomain.domain.com
      http:
        paths:
        - path: /
          pathType: Prefix
          backend:
            service:
              name: admin-fe-service
              port: 
                number: 80

Nginx on the docker image default.conf

upstream adminBackend {
    server admin-be:8080;
}

server {
  listen 80;
  listen [::]:80;
  server_name subdomain.domain.com;

    location / {
    root /usr/share/nginx/html;
    index index.html index.htm;
    try_files $uri $uri/ /index.html =404;
    }

    location /app {
    proxy_pass http://adminBackend;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $host;
    proxy_pass_request_headers on;
    proxy_http_version 1.1;
  }
}

Log from nginx-ingress-controller pod

kubectl describe ingress admin-fe -n development