Hi @rgreen, welcome to the community!
From reading this thread over in Webflow’s forum, it seems this is a limitation of their API:
(…) you need to do with the live = true param with ONLY the base required fields that the system assigns to the collection: In my case (standard CMS collection), that would mean: name, slug, _draft & _archived.
So you probably need to play a bit with your fields and remove some of them when using the Live option before this works.