My backend is not working after adding the SSL certificate. The backend worked with http before but after adding SSL certificate it stopped working. I thought the problem is with nginx configurations but I think the problem is not in that but something else. My back is developed on nestjs

server {
    listen 443 ssl;
    server_name example www.example;

    ssl_certificate /etc/letsencrypt/live/example/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example/privkey.pem;

    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_ciphers 'TLS_AES_128_GCM_SHA256:TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-A>

    root /var/www/html;
    index index.html index.htm;

    add_header Strict-Transport-Security "max-age=31536000" always;
    add_header Content-Security-Policy upgrade-insecure-requests;

    # frontend
    location / {
        proxy_pass http://127.0.0.1:3000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
    # backend
    location /api/ {
        proxy_pass https://127.0.0.1:5001/; 
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
    }
}

main.ts

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import * as fs from 'fs';
import * as https from 'https';

async function bootstrap() {
  const httpsOptions = {
    key: fs.readFileSync('/etc/letsencrypt/live/example/privkey.pem'),
    cert: fs.readFileSync('/etc/letsencrypt/live/example/fullchain.pem'),
  };

  const app = await NestFactory.create(AppModule, {
    httpsOptions,
  });

 await app.listen(5001, () => {
  console.log('Server is running on https://localhost:5001');
 });

}
bootstrap();

NGINX LOGS

2025/01/17 17:05:07 [error] 325374#325374: *278 connect() failed (111: Unknown error) while connecting to upstream, client: 149.154.161.248, server: example, request: "GET /api/ HTTP/1.1", upstream: "https://127.0.0.1:5001/", host: "example"
2025/01/17 17:05:17 [error] 325374#325374: *280 connect() failed (111: Unknown error) while connecting to upstream, client: 80.242.211.179, server: example, request: "GET /api/ HTTP/1.1", upstream: "https://127.0.0.1:5001/", host: "example", referrer: "/"
2025/01/17 17:05:22 [error] 325374#325374: *280 connect() failed (111: Unknown error) while connecting to upstream, client: 80.242.211.179, server: example, request: "GET /api/hello HTTP/1.1", upstream: "https://127.0.0.1:5001/hello", host: "example"
2025/01/17 17:06:08 [error] 325374#325374: *284 connect() failed (111: Unknown error) while connecting to upstream, client: 149.154.161.201, server: example, request: "GET /api/ HTTP/1.1", upstream: "https://127.0.0.1:5001/", host: "example"
2025/01/17 17:06:28 [error] 325374#325374: *280 connect() failed (111: Unknown error) while connecting to upstream, client: 80.242.211.179, server: example, request: "GET /api/hello HTTP/1.1", upstream: "https://127.0.0.1:5001/hello", host: "example"
2025/01/17 17:06:28 [error] 325374#325374: *280 connect() failed (111: Unknown error) while connecting to upstream, client: 80.242.211.179, server: example, request: "GET /api/hello HTTP/1.1", upstream: "https://127.0.0.1:5001/hello", host: "example"
2025/01/17 17:06:29 [error] 325374#325374: *280 connect() failed (111: Unknown error) while connecting to upstream, client: 80.242.211.179, server: example, request: "GET /api/hello HTTP/1.1", upstream: "https://127.0.0.1:5001/hello", host: "example"
2025/01/17 17:06:29 [error] 325374#325374: *280 connect() failed (111: Unknown error) while connecting to upstream, client: 80.242.211.179, server: example, request: "GET /api/hello HTTP/1.1", upstream: "https://127.0.0.1:5001/hello", host: "example"
2025/01/17 17:06:29 [error] 325374#325374: *280 connect() failed (111: Unknown error) while connecting to upstream, client: 80.242.211.179, server: example, request: "GET /api/hello HTTP/1.1", upstream: "https://127.0.0.1:5001/hello", host: "example"
2025/01/17 17:07:09 [error] 325374#325374: *297 connect() failed (111: Unknown error) while connecting to upstream, client: 149.154.161.218, server: example, request: "GET /api/ HTTP/1.1", upstream: "https://127.0.0.1:5001/", host: "example"

I checked if the ports and queries are working correctly via curl -v at the end of the query the following message is displayed

{"message":"Cannot GET /","error":"Not Found","statusCode":404}

I've tried changing permissions on ssl certificates to make it work, changed nginx configuration thinking that's the problem but it's the backend that still doesn't work.