Root certificate expired

@zguoqi Your site is using a very old "R3" chain:

Certificate chain
 0 s:/
   i:/C=US/O=Let's Encrypt/CN=R3
 1 s:/C=US/O=Let's Encrypt/CN=R3
   i:/O=Digital Signature Trust Co./CN=DST Root CA X3

See this for an explanation of the two current chains. You should choose one of these.

Please answer the other questions you were shown when posting. This will help us guide you better. Thank you

Please fill out the fields below so we can help you better.

My web server is (include version):

The operating system my web server runs on is (include version):

My hosting provider, if applicable, is:

I can login to a root shell on my machine (yes or no, or 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):

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