Unable to connect to Home Assistant 502 bad gateway

I’m using a reverse proxy letsencrypt and im unable to access via the internet after my server restarted. need help troubleshooting.

This is the error logs:

 2020/06/04 23:20:36 [error] 416#416: *54 homeassistantcore could not be resolved (3: Host not found), client: 192.168.1.254, server: nomansland.ddns.net, request: "GET /api/websocket HTTP/1.1", host: "nomansland.ddns.net"
 2020/06/04 23:20:39 [error] 416#416: *51 connect() failed (113: Host is unreachable) while connecting to upstream, client: 192.168.1.254, server: nomansland.ddns.net, request: "GET / HTTP/2.0", upstream: "http://192.168.1.201:8123/", host: "nomansland.ddns.net"
 2020/06/04 23:20:39 [error] 416#416: *51 connect() failed (113: Host is unreachable) while connecting to upstream, client: 192.168.1.254, server: nomansland.ddns.net, request: "GET /hacsfiles/iconset.js HTTP/2.0", upstream: "http://192.168.1.201:8123/hacsfiles/iconset.js", host: "nomansland.ddns.net", referrer: "https://nomansland.ddns.net/"
 2020/06/04 23:20:39 [error] 416#416: *51 connect() failed (113: Host is unreachable) while connecting to upstream, client: 192.168.1.254, server: nomansland.ddns.net, request: "POST /auth/token HTTP/2.0", upstream: "http://192.168.1.201:8123/auth/token", host: "nomansland.ddns.net", referrer: "https://nomansland.ddns.net/"
 2020/06/04 23:20:39 [error] 416#416: *51 connect() failed (113: Host is unreachable) while connecting to upstream, client: 192.168.1.254, server: nomansland.ddns.net, request: "GET /manifest.json HTTP/2.0", upstream: "http://192.168.1.201:8123/manifest.json", host: "nomansland.ddns.net", referrer: "https://nomansland.ddns.net/lovelace"
 2020/06/04 23:20:39 [error] 416#416: *51 connect() failed (113: Host is unreachable) while connecting to upstream, client: 192.168.1.254, server: nomansland.ddns.net, request: "GET /service_worker.js HTTP/2.0", upstream: "http://192.168.1.201:8123/service_worker.js", host: "nomansland.ddns.net", referrer: "https://nomansland.ddns.net/service_worker.js"

and this is my config

 server {
     listen 443 ssl;
     listen [::]:443 ssl;
 
     server_name nomansland.ddns.net;
 
     include /config/nginx/ssl.conf;
 
     client_max_body_size 0;
 
     location / {
 
         include /config/nginx/proxy.conf;
 		proxy_pass http://192.168.1.201:8123;
 
     }
 
     location /api/websocket {
 		proxy_pass http://192.168.1.201:8123;
 
         proxy_set_header Host $host;
 
         proxy_http_version 1.1;
         proxy_set_header Upgrade $http_upgrade;
         proxy_set_header Connection "upgrade";
     }
 }