curl loopback error 28

When I run health check on my wordpress server (that I host myself), I get the following error:

The loopback request to your site failed, this may prevent WP_Cron from working, along with theme and plugin editors.
Error encountered: (0) cURL error 28: Operation timed out after 10001 milliseconds with 0 out of -1 bytes received

I do not get an error when I run curl -vvI https://www.example.com. Any idea why I might be seeing that error within health check?

I’m also seeing this:

Couldn’t retrieve a list of the checksums for WordPress 4.9.8. This could mean that connections are failing to WordPress.org.

Not sure if it’s related.