Resolving SSL related errors would be bit tricky for non-technical users and UNABLE_TO_VERIFY_LEAF_SIGNATURE is one of the common error you could face while installing SSL certificate on your cPanel or hosting platform.
UNABLE_TO_VERIFY_LEAF_SIGNATURE error during SSL installation is caused primarily due to invalid or mismatched intermediate certificate / CA Bundle thus failed chain of trust. Since you are trying to install Let’s Encrypt (Open certificate authority) SSL certificate, chances are you missed their new update regarding the new root & intermediate certificates and trying to install wrong intermediate certificate for your site.
Fixing the UNABLE_TO_VERIFY_LEAF_SIGNATURE issue
- Login to your wp-admin, go to PLUGINS > ADD NEW.
- Install and activate “WP Encryption” free SSL plugin.
- If already installed, please make sure to update the plugin to latest version.
- Click on WP Encryption tab on left panel in your wp-admin and you will notice SSL install form.
- Enter your email in SSL install form and click on Generate SSL button.
- Verify your domain ownership via HTTP or DNS method.
- After success, You can copy the newly generated Certificate.crt, Private.pem and CA Bundle / Intermediate Certificate for your site.
- Paste these 3 into its appropriate input fields on SSL installation page of your cPanel / hosting panel.
- SSL installation should succeed and your HTTPS site should start working.
P.S., If you are using WP Encryption Pro version – Please update the PRO plugin to latest release (We continuously test the whole process and push updates ASAP in case of any error / new protocol ), use RESET option of WP Encryption and re-run the SSL install form once, Your SSL installation will succeed instantly.