Hello AdamU27,
Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.
If you reformat those to "cf:location" and "cf:employeetype" it should resolve the issue and populate the custom fields correctly for the contacts you are adding.
When you call GET /contact_custom_fields, you’ll notice it returns the value for the property "label” as the custom field appears in the UI, but the property for "name" returns a value that has removed any uppercase letters and replaced spaces with underscores.
GET custom_fields Collection
https://v3.developer.constantcontact.com/api_reference/index.html#!/Contacts_Custom_Fields/getCustomFields
Please have a look and let us know if you have any other questions!
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