You need to provide more information or it will be hard to help you.

1, Is dev-server.com a public domain? If so, the problem may be with the DNS resolution. By default Docker containers use the host's DNS address. You can check the DNS address in the following ways.

docker exec -it container_id bash
cat /etc/resolv.conf

Or in the nginx configuration via

http {
    resolver 8.8.8.8;
}

to specify one manually.

2, Is dev-server.com another container? If so, you need to put both containers under the same docker network.