wp_remote_post may use cURL as the underlying technology. cURL doesn’t have an in-built certificate, like all the browsers and relies on external certificates to verify SSL of websites. In majority of setups things just work fine and you don’t need to worry much about it.
But in some cases, connecting to websites over
https fails because of missing or incorrect cURL. In this regard, we need to point PHP cURL to use the correct one.
wget https://curl.haxx.se/ca/cacert.pem mv cacert.pem /etc/php7.0/cacert.pem
Now edit your php.ini file. If you are on a dedicated or VPS server, then you know which file to edit (or your sysadmin knows). If on a shared server, then I highly recommend to get help from your webhost support. If you are feeling geeky, then use this guide to find out how to locate your php.ini file.
Now place/modify the following directive.
You can store the files anywhere and refer to the absolute path. Once done, save the ini file and restart the server.
sudo systemctl restart php7.0-fpm
sudo systemctl restart apache2.service