Custom Fields - The custom fields are considered 'active', and will now be available only on the test site. You need to publish the fields to your live site to include custom field information in the invoices that you send to your customers, or in the hosted pages viewed by them. Ensure that you check how the fields work for all your use cases before pushing it to your live site.

On the Custom Fields main page, click Publish to Live and confirm changes. The custom fields will now be available on your LIVE site.

For more details, please refer - https://www.chargebee.com/docs/custom_fields.html#creating-custom-fields

You can configure the custom fields by navigating to Settings > Configure Chargebee > Invoices, credit notes, and quotes > Invoices > Enable: Custom fields.