Internal error when generating ssl certificate Synology NAS Docker

I'm trying to generate a ssl certificate for my Portainer docker container. In the past this all went well, but after an update to my Synology NAS (DSM 7.1-42661 Update 4) I needed to re-instal the NGINX Proxy Manager running via docker (compose) (managed via Portainer). Adding a proxy host is fine, but when I want to generate a new ssl certificate, I get this error message in the Portainer log:

An unexpected error occurred:

requests.exceptions.ConnectionError: HTTPSConnectionPool(host='', port=443): Max retries exceeded with url: /directory (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7f71df89d278>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution'))

My domain is: (

My web server is (include version): v2.9.18

The operating system my web server runs on is (include version): Synology NAS (DSM 7.1-42661 Update 4), with Docker (20.10.3-1308)

My hosting provider, if applicable, is: duckdns

I can login to a root shell on my machine (yes or no, or I don't know): I don't know

I'm using a control panel to manage my site (no, or provide the name and version of the control panel): Portainer (2.14.2)

The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot): 1.25.0

What can I do to solve this issue?

Thanks in advance

1 Like

Please fix the DNS resolving capabilities in the appropriate environment your ACME client is running in.


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