Please check if the self-request is not blocked on your server?

Also, check if the abc.com server is able to find out/locate the abc.com
It might happen that on the abc.com the requests are blocked to self-domain using htaccess file.

To Check this create a test.php file on abc.com server and send the curl request to that domain.

The code for the same is as follows:

$url = 'http://abc.com/';
$useragent = 'Opera/9.80 (J2ME/MIDP; Opera Mini/4.2.14912/870; U; id) Presto/2.4.15';
$ch = curl_init('');
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_USERAGENT, $useragent); // set user agent
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
echo $output = curl_exec($ch);
curl_close($ch);
echo $contents;
$url="http://abc.com/lms"

Add the above code in test.php and check it’s output. If it shows abc.com/lms Homepage then please contact us so that we can check the issue on your end.

If the above code output gives an error that means the sites are not able to connect to each other probably because the request is being blocked from the other site. In most of the cases, if the WordPress and Moodle site are on the same server then ask the hosting providers to enable requests from the same server to fix this issue.