cURL error

What web server are you testing with?

See https://drupal.org/project/commerce_paypal at the bottom:

If your PayPal API requests are failing due to SSL certificate verification, refer to the comments in the cURL request preparation of commerce_paypal_api_request() to read how to specify a local CA certificate bundle file.

From commerce_paypal_api_request():

Commerce PayPal requires SSL peer verification, which may prevent out of
date servers from successfully processing API requests. If you get an error
related to peer verification, you may need to download the CA certificate
bundle file from http://curl.haxx.se/docs/caextract.html, place it in a
safe location on your web server, and update your settings.php to set the
commerce_paypal_cacert variable to contain the absolute path of the file.
Alternately, you may be able to update your php.ini to point to the file
with the curl.cainfo setting.

I downloaded the file from http://curl.haxx.se/docs/caextract.html, added the line below to settings.php and it was resolved:

$conf['commerce_paypal_cacert'] = 'D:\wamp\apps\curl\cacert.pem';

Same issue here, cURL error with PayPal API requests failing due to SSL certificate verification.

Downloading the download the CA certificate bundle file and setting the commerce_paypal_cacert variable worked for my local setup, which is XAMPP version 1.7.7.

How to do I test if this is required on my live site?

My live site is working fine on Commerce PayPal 1.0, is the 2.2 module likely to be broken in this way?

Anything I can look for in phpinfo() to see if this fix is needed on the live server?

Thank you!

Thanks for following up here. I'd just give it a shot and see what happens. If you're running in a reasonably modern hosting environment for your live site, it should resolve those SSL certificates just fine. If not, it's a quick process to make it work.

How about only enabling the verify peer option for live transactions?

<?php
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, $payment_method['settings']['server'] == 'live');
?>