I entered the API key in the HTTP header, but I'm getting NOT_FOUND_APIKEY / INVALID_HTTP_HEADER errors.

When defining the API key in the HTTP header, you must adhere to the following standard:

Correct request format: curl -H "apikey: ABC1G2..." -XGET https://api.neople.co.kr/df/servers

Incorrect request formats: curl -H "apikey : ABC1G2..." -XGET https://api.neople.co.kr/df/servers curl -H "apikey :ABC1G2..." -XGET https://api.neople.co.kr/df/servers