Hi @nayeem_riddhi, I checked deactivating all the plugins in our dev website and still had the same issue.
I started googling a little bit about the mysql_real_escape_string function and realized what the issue is.
We are using PHP 7.4 for this WP install, and according to the PHP.net documentation, the mysql_real_escape_string function was deprecated in PHP 5.5, then eliminated in PHP 7.0. This function has been replaced by mysqli_real_escape_string
In the plugin code, this is found in the campaign/util/subscriberlist.php file, in lines 182, 183 and 184.
Can you release to us a test version of the plugin with these modifications to confirm if this fixes the problem?
