API returns null

[Haisfbmi2019]

Good afternoon, the API for JAVA does not work for me, it returns null for all requests with authentication

[Haisfbmi2019]

    BithumbProApiRestClient restClient = new BithumbProProApiRestClientImpl(
            "--",
            "--"
    );
    System.out.println(restClient.assets(null, "spot").getData().toString());
    
    Console :
    null
    
    and I have such errors with every request except the ticker and system time