OpenSSL uses an SSL certificate to encrypt data passed via cURL. If you test X-Cart on a local machine and your web server does not have an SSL certificate, your store will not connect to the X-Cart App Store. If this is your case, you need to generate a self-signed SSL certificate to install add-ons. How you can do it will depend on what type of server you are using.
Creating a Self-signed SSL Certificate
Windows + XAMPP
Download latest cacert.pem file from cURL’s website http://curl.haxx.se/docs/caextract.html
Save it as you wish, for instance, C:\Windows\ca-bundle.crt. But, yes, you need to change its extension from .pem to .crt.
Add the following line to your xampp\php\php.ini file under the [PHP] header
curl.cainfo = c:\windows\ca-bundle.crt
Restart Apache and this certificate file should be picked up properly.
Windows + WAMP
The same instruction as above, except you need to edit the wamp\bin\apache\apache2.4.9\bin\php.ini file instead of xampp\php\php.ini one.