Custom Field API

Hi all.
I create contact with API
But i see ERROR: 10 - [NoFieldFound]No field found: Contact.mahang

Help me!

A little more detail would help me help you. Would you let me know which API you’re using, which endpoint/service, etc? Also, would you provide the HTTP request and payload you’re sending to the API? (Be sure to remove any sensitive bits you wouldn’t want to share publicly.) Thanks

Thank you for help.

I use iSDK GitHub - ksnider/iSDK: This is a clean copy of the deprecated Infusionsoft SDK (pre-oAuth)
I have config file like that

<?php $connInfo = array('connectionName:applicationName:i:APIKEYGOESHERE:This is the connection for'); ?>

But i create new contact with normal field IS is correctly, and i try create new contact with custom field but not worked.
I use View the field database names (for the API) but don’t work
Please help!

Mahang would have to be a custom field. If that’s what you’re looking to write to then the field name must be preceeded by an underscore as in _mahang