extima

with 2.1.14 and WordPress 5.1, when entering the API key we were getting the curl error. It was a new build and so we did not try previous versions of WP with 2.1.14.
Rolling back to 2.1.11 and staying on WP 5.1 worked.
We did not test 2.1.12 or 2.1.13 – we went all the way back to 2.1.11 because it sounded like that is what people had success with.
Our store was able to sync properly after that – orders/products are up to date.

We also have same problem with version 2.1.14, downgraded to 2.1.11 and it works fine. Running PHP 7.2 WordPress 5.1. Spent a lot of time trying to figure out what was wrong with curl on the server side and/or security (CloudFlare, WordFence) but it was just the plugin. Thank you for tip on downgrading!

Rackspace Coudsites has a 30 second timeout limit at the Load balancer and there is not much we can do that I know of to change that.
https://www.rackspace.com/knowledge_center/article/connection-timeout-error-message-on-cloud-sites

The part of the code that is timing out is a call to see if the remote files need to be pulled back down to the local. I am personally using this 1-way (posting TO the CDN) and do not need the 2-way sync and so I commented out the code to see if any files need to be pulled back down and now it runs.
WARNING: If you delete files from local, you will not be able to turn that feature off and get the files to auto-pull back down. If you ever need those files again, you will have to grab them with CyberDuck or similar.
line 275 – comment

//$remote_objects = $_SESSION['cdn']->get_cdn_objects(true);

Then again around line 290 – the note above said line 284, but we may be on different versions. I am using version 1.3.1 of the plugin

// Check remote files needing DOWNloaded
	//foreach ($remote_objects as $cur_remote_object) {
	//	if (!in_array($cur_remote_object, $local_objects) && $cur_remote_object['fs'] > 0) {
	//		$cdn_url = (isset($_SESSION['cdn']->api_settings->use_ssl)) ? get_cdn_url('ssl') : get_cdn_url();
	//		$cur_remote_object['fn'] = $cdn_url.'/'.$cur_remote_object['fn'];
	//		$objects_to_download[] = $cur_remote_object;
	//		$objects_to_download[] = ''
	//	}
	//}

If anybody can figure out how to get this script to run faster or return ajax updates so that the load balancer sees activity, that would be a huge help.

I was having the same problem. I updated to wordpress 3.3 and that seems to have fixed the issue.