WordPress.com REST API sporadically returning "unknown_blog" error

I am having intermittent trouble with the REST API returning “unknown_blog” errors, but at other times it works just fine. I can’t find a pattern.

The site in question is hosted on wordpress.com, and the URL is http://stepuphouston.com/

When I access https://public-api.wordpress.com/rest/v1/sites/stepuphouston.com/posts?pretty=1&type=page , I will sometimes get the correct JSON output, but other times will get the following message:

{ "error": "unknown_blog", "message": "Unknown blog"}