[Plugin: wpCJ Chimp] Unable to retrieve mailing lists from MailCHimp

I could resolve this by modifying
$lists_array = $MCHandler->lists($apikey);
to $lists_array = $MCHandler->lists();

in wpcj-chimp/index.php
This is the correct way according to the mailChimp API wrappers, btw.

You can check if there’s an error by using

if ($MCHandler->errorCode){
	echo "Unable to load lists()!";
	echo "\n\tCode=".$MCHandler->errorCode;
	echo "\n\tMsg=".$MCHandler->errorMessage."\n";
}

Which in my case allowed me to see that the Datacenter being used was the wrong one (the -us2 or -us1 after your API key). So I headed to wpcj-chimp/MCAPI.class.php and I just changed in line 42:

$this->apiUrl = parse_url("http://api.mailchimp.com/" . $this->version . "/?output=php");

To

$this->apiUrl = parse_url("http://us2.api.mailchimp.com/" . $this->version . "/?output=php");

You can just put your datacenter before the .api there.

Note that I don’t think this is the proper way to define your datacenter when using the mailChimp API, so you’re welcome to look for a better method that doesn’t alter the MCAPI.class.php.