Clients has been renamed to Applications a few days ago, however, the doc response 404.
$ curl https://auth0.com/docs/applications -IL
HTTP/2 301
[...]
location: /docs/clients
[...]
HTTP/2 404
[...]
I can see the contents under the applications(like Connections), so I guess Overview is the only problem.
$ curl https://auth0.com/docs/applications/connections -IL
HTTP/2 200