To secure connections with external resources, WordPress uses a file called "CA bundle (ca-bundle.crt)", usually located in "/wp-includes/certificates/", which contains a list of recognized certificate authorities to confirm that an SSL certificate is legitimate.
If this file is missing, corrupted, or outdated, WordPress cannot establish a secure connection, resulting in this error:
curl: (60) SSL certificate problem: unable to get local issuer certificateThe "cURL (60)" error indicates that WordPress is unable to verify the validity of a remote server's SSL certificate during an HTTP request.
The most common causes are an outdated certificate bundle or using an outdated version of WordPress.
To resolve the issue, it is recommended to replace the contents of the ca-bundle.crt file with a recent version from this link via the cPanel file manager while checking the file permissions, and then ensure that the server's SSL configuration is correct, with a complete certificate chain including the server certificate, intermediate certificates, and root certificate.