I had a similar issue as the thread-starter and I also did create a subdomain in Yunohost with Adding the www entry to the DNS settings in the hosting provider. www.mywebsite.org . However, I’ve got the certificate issue when trying to access www.mywebsite.org. https://mywebsite.org worked fine.
I’ve tried all sorts of things, like removing and re-adding the domain.
Problem was that I could not generate a certificate for www.mywebsite.org . The green button was inactive.
At the end I did run Yunohost diagnostics and after that it was possible to generate the let’s encrypt certificate. The green button became active. After generating the certificate, I could access the www.mywebsite.org without getting a certificate error.
I’m wondering why this procedure is not mentioned in the Yunohost DNS documentation? Or did I just didn’t find it? Is it not common to configure a www subdomain in Yunohost?
In my opinion it should be in the YH doc’s.