www subdomain works but others don't

I encountered a problem with nginx I do not understand.

I am able to correctly setup and call www.example.tech and example.tech.

However when adding another subdomain like survey.example.tld to the list the other two still work but survey.example.tld does not.

In chrome I get the following error message when trying to call http://survey.example.tech/:

This site can’t be reached Check if there is a typo in survey.example.tech. DNS_PROBE_FINISHED_NXDOMAIN

I am pretty sure there is no typo in it because I triple checked. Also, www.example.tech and example.tech still work.

I use nginx to forward requests to a gunicorn/flask app.

Therefore I put my config into /etc/nginx/sites-enabled

$ cat /etc/nginx/sites-enabled/survey.example.tech 

server {    
    server_name example.tech www.example.tech survey.example.tech;
    
    location /static {
        alias /opt/example.tech/my-domain-Survey-Website/static;
    }
    
    location / {
        proxy_pass http://localhost:8003;
        include /etc/nginx/proxy_params;
        proxy_redirect off;
        # Max file size allowed for upload by user. Here 1M = 1 Megabyte
        client_max_body_size 1M;
        
        # prevents warning messages when setting up let's encrypt
        proxy_headers_hash_max_size 512;
        proxy_headers_hash_bucket_size 128;
        
        # Enable Websocket by adding these two options
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
    }
}

and the corresponding service in /etc/systemd/system

$ cat /etc/systemd/system/gunicorn-my-domain-survey-flask.service 
[Unit]
Description = gunicorn for my-domain website
After = network.target

[Service]
Environment=LOG_PATH=/opt/example.tech/example.tech-Survey-Website/gunicorn-logs
User = ubuntu
Group = ubuntu
WorkingDirectory = /opt/example.tech/example.tech-Survey-Website
ExecStart = /opt/example.tech/venv/bin/gunicorn --bind 127.0.0.1:8003 -w 1 --log-level debug --access-logfile ${LOG_PATH}/access-logfile.log --error-logfile ${LOG_PATH}/error.log  --capture-output run_survey_website:app

[Install]
WantedBy = multi-user.target

When I run this everything works fine except for survey.example.tech.

What is happening here? Am I missunderstanding the setup of subdomains with nginx?