I think you are trying to call the methods from Unity_Editor, if you are doing so then you have to use X509Certificates validator like this :-
#if UNITY_EDITOR
public static bool Validator (object sender, System.Security.Cryptography.X509Certificates.X509Certificate certificate, System.Security.Cryptography.X509Certificates.X509Chain chain, System.Net.Security.SslPolicyErrors sslPolicyErrors)
{return true;}
#endif
void Start ()
{
#if UNITY_EDITOR
ServicePointManager.ServerCertificateValidationCallback = Validator;
#endif
App42API.Initialize("API_KEY","SECRET_KEY");
}
This is also mentioned in README of the SDK.
If your issue still exists or any other query, feel free to ask us.