Renew error - The ACME service (directory) is unavailable

The renewal of my certificate crashes with this error:
[ERR] The ACME service (directory) is unavailable.
But during a test everything is ok.
To my knowledge no change on the server has taken place. : Extensionless File Config Test - OK (but insecure) : ERR_CONNECTION_REFUSED

2021-11-15 10:07:56.211 +01:00 [INF] All Tests Completed OK
2021-11-15 10:07:58.692 +01:00 [INF] ---- Beginning Request [My Site] ----
2021-11-15 10:07:58.692 +01:00 [INF] Certify/ (Windows; Microsoft Windows NT 10.0.17763.0)
2021-11-15 10:07:58.699 +01:00 [INF] Beginning Certificate Request Process: My Site using ACME Provider:Certes
2021-11-15 10:07:58.699 +01:00 [INF] Requested identifiers to include on certificate:
2021-11-15 10:07:58.700 +01:00 [INF] Beginning certificate order for requested domains
2021-11-15 10:07:59.170 +01:00 [ERR] The ACME service (directory) is unavailable.



Let’s Encrypt did have some server maintenance today ( however if the problem persists can you please check that you are able to browse to using IE (or Edge/Chrome) on your server. This is the API endpoint the application needs to communicate with.

There are various other possible reasons why your server would fail to communicate (supported TLS cipher settings, firewall blocking outgoing https etc).