Using the the Formidable Forms API with on WP site hosted at Wordpress.com I am trying to write entries into an existing form from an outside source.  I am receiving the following json back. 
{"code":"rest_forbidden_context","message":"Sorry, you are not allowed to create entries","data":{"status":403}}
I am using the following endpoint:
https://mysite.com/wp-json/frm/v2/forms/18/entries
I have verified that I am passing the correct api key.
I have installed the Formidable Logs add-on but it only seems to track the outbound actions.
I tried temporarily disabling my site security and still get the same error.  I also tried this from Postman and am getting the same error. 
Thoughts?  Is there a snippet I need to add to allow the endpoint to be written too?
Thanks.