Webmin is failing to use the LetsEncrypt SSL certificate generated from "SSL Encryption" section.

Steps taken to cause problem:

1. Verified apache configuration is correct and working.
2. Go to webmin/edit_ssl.cgi > Let's Encrypt
3. Verify "Copy new key and certificate to Webmin?" set to Yes. Set all other options. Successfully generate SSL certificate.
4. Restart webmin, still using default self-signed certificate.
5. Restarted server. No change. Verified issue exists on multiple computers (not a cache issue)

Troubleshooting performed.

1. Check directory:
root@hostname:/etc/webmin# ls -la lets*
-rw------- 1 root root 1647 Nov  7 20:37 letsencrypt-ca.pem
-rw------- 1 root root 2151 Nov  7 20:37 letsencrypt-cert.pem
-rw------- 1 root root 3247 Nov  7 20:37 letsencrypt-key.pem
2. Verified files are correct, valid and working.
3. Go back to webmin/edit_ssl.cgi, go to SSL Settings, verified settings are correct. The settings were already filled out properly. Hit Save, get error:
"Failed to save SSL options : The SSL private key file /etc/webmin/letsencrypt-key.pem does not exist or does not contain a PEM format key"
4. run chmod 777 /etc/webmin/letsencrypt-key.pem. Error still occurs. Revert chmod.

Possible cause: pem check is incorrect and causing webmin to use default miniserv certificate.