Getting 403 error from Site Health tools for the REST API

From Site Health Tools, I am getting the following:

“When testing the REST API, an unexpected result was returned:

REST API Endpoint: https://www.ism-houston.org/wp-json/wp/v2/types/post?context=edit
REST API Response: (403) Forbidden”

If I go to URL above I get this:

{"code":"rest_forbidden_context","message":"Sorry, you are not allowed to edit posts in this post type.","data":{"status":401}}

I am also getting loopback requests could not be completed.

I am also getting a similar issue from WP Super Cache. Support there responded with the following:

The loopback request issues in conjunction with the 403 errors most likely indicate that your webserver configuration prevents internal requests.
A misconfiguration of BasicAuth is one of the most common ones. I would recommend that you check that with your host.

I contacted the hose, Digital Space, listing the issues I am having and they just respond with the comment that all is well with my site and database. They don’t answer if their server configuration prevents internal requests.

Is there a way to conclusively show one way or the other if their servers are preventing any kind of internal requests? What log do I got to find this and how do I recognize this?

Thanks for the help.