While working with Zapier to send data to a Webflow Collection, repeatedly received errors that were not particularly helpful. After help from an individual with more coding capabilities than me, learned that Webflow was looking for the original field names and not the current field names. On the positive side, this means that one doesn't need to worry about breaking integrations if field names change as it remains what the field was originally. But it also means that one must remember the original field name -- or know how to use tools like Postman.
This Twitter thread from Tony Gines contains additional information:
A request to show labels and field names has been submitted to the Webflow Wishlist.