I recently was annoyed by a strange error.
„Failed to connect to Let’s Encrypt. Please make sure your Diskstation and router have port 80 open to Let’s Encrypt domain validation from the Internet. All other communications with Let’s Encrypt go over HTTPS to keep your Diskstation secure.“
Is was searching for port forwarding issues on port 80 and 443. But seems all correct and working. Must be something else. Finally found the root cause.
The website was reachable using www sub- domain prefix but not without. Using mathiasirmer.com there was a not working redirection. As soon as I fixed this I was able to get the certificate from Lets Encrypt. So don’t let this error message guide you in the wrong way.
Do you see this issue and need help? Leave me a comment!