Renew

1. sudo systemctl stop apache2
2. For pi4, change back the dilink wifi router port forward for internet inbound 80 and 443. 

   
   
   
3. sudo certbot renew
4. sudo systemctl start apache2
5. For pi4, change the dilink wifi router port forward for internet inbound 9680->80 and 9681->443  

   
   
   

Use the command to check the certificate date:

echo | openssl s_client -connect localhost:443 -servername kpchiao9600k.sino.tw 2>/dev/null | openssl x509 -noout -dates

One more thing:

Just wait until the end of 3-month period to renew, because the next expiration date is counted from the renew date.