The connection is not secure

[3rink]

Hi, I'm new to the topic and don't know what to do next. After days of trying it out, I finally made it. I have a domain pointing to my host. I have a working NPM. Unfortunately, the certificates are not secure and I don't know what's wrong.
It would be great if you can help me to solve the last problem to finally get my little NAS to run.

[thegolikov]

To add an SSL certificate for a domain, go to the domain settings in NPM and go to the SSL section. There is an opportunity to issue a free LetsEncrypt certificate. Don't forget to enable forced SSL, HTTP/2, and HSTS support.

[3rink]

Hi, I did that. The connection is displayed as insecure. What else can I do?
I got this:
net::ERR_CERT_COMMON_NAME_INVALID

[thegolikov]

Are you sure that the domain has received a certificate? Can you attach screenshots of the Details, SSL tabs?