Netlify default subdomain doesn't have HTTPS

I’m trying to access https://loupe-staging.netlify.app

It used to work before, but I’m not sure what changed and now I’m getting the “Your connection is not private” error from Chrome.

When I go to the Domain Management > HTTPS section, I see this:

The only custom domain is the default one: loupe-staging.netlify.app

Nothing has changed since it last used to work. How do I fix this?

The same is also true for https://loupe.netlify.app, although its custom subdomain https://www.loupehealth.com works.

To make this stranger, I get this error on my laptop (both Chrome and Safari), but a person next to me on a different laptop on the same network gets through to the site fine. When I updated my Chrome, it works now on Chrome (and Firefox), but Safari still does not work.

It still works fine for me across all my devices - this sounds to me like a local configuration issue.