Nginx adding certificate worked but renew dry-run fails

[MikeMcQ]

@matthttam

Certbot failed to authenticate some domains (authenticator: nginx). The Certificate Authority reported these problems:
  Domain: inventory.owensboro.kyschools.us
  Type:   connection
  Detail: During secondary validation: 170.185.177.50: Fetching http://inventory.owensboro.kyschools.us/.well-known/acme-challenge/*randomstring*: Timeout during connect (likely firewall problem)

Hmm. It looks like there is a firewall that blocks access from IP addresses outside the US. But, it is puzzling how you got a cert earlier today which would have required access from the Let's Encrypt Server in Germany (they might move around but various points around the world are used).

Could you have changed a firewall setting after getting the cert?

See this global test site for only US connection worked

I have no trouble accessing from my US test server and Let's Debug test site was fine too. The error saying "Secondary Validation" failed indicates it may have been the Europe region failing.