Timeout during connect (likely firewall problem)

[MikeMcQ]

@maverickws

Certbot failed to authenticate some domains (authenticator: apache). The Certificate Authority reported these problems:
  Domain: domain-xyz.com
  Type:   connection
  Detail: 100.200.300.400: Fetching http://domain-xyz.com/.well-known/acme-challenge/dKUUKpTa0HO0jc8hybW8hpqc9-2JQ3tCXq8eFlE7LDo: Timeout during connect (likely firewall problem)

This error is a "Timeout". Meaning the Let's Encrypt server could not reach your domain.

Your examples using curl showed a 404 and 200 response. Both of those were successful connects just with different reply. Neither is a timeout. Are you sure you were testing from outside your network?

The Let's Debug test site is often helpful to debug

Without further details there is not much to say. A timeout is most often a firewall issue