Why this error?
Transfer of sensitive information is typically done under the cover of digital certificates. The certificate will help confirm to the recipient that the sender is actually who they claim they are. Digital certificates are issued by certificate authorities.
A list of trusted certificate authorities and their root certificates are installed on a server when a digital certificate is applied to the server. Transactions over regular HTTPS will revert to this list for communication. However, CURL does not follow the rules. You need to tell curl about the ca root certificates.
How to resolve?
To resolve the error, you need to define your CURL certificate authority information path
To do that,
Download the latest curl recognized certificates here: https://curl.haxx.se/ca/cacert.pem
Save the cacert.pem file in a reachable destination.
Then, in your php.ini file, scroll down to where you find [curl].
You should see the CURLOPT_CAINFO option commented out. Uncomment and point it to the cacert.pem file.