Hi,
In version 2.0.2 I disabled by default support of REST API because it was causing a lot of issue with other plugins in backend.
To enable the support with REST API you need to pass wpessid in REST request with ID (for specific search setting) or without ID (for global search setting).
You can contact the facetWP support to know how to modify search request and add a parameter. (This is a paid plugin and I can’t see the code to help you, sorry.)
Thanks
Thanks a lot for the reply, will get in touch with FacetWP for this!