Ben: It seems that the reason for this error is the latest WordPress version 4.6. I found this solution: https://wordpress.org/support/topic/read-this-first-wordpress-46-master-list?replies=5#post-8770164, but it seems that is not working.
User: I upgraded everything yesterday and now have this error message at the top of my event pages -- http://charmedinlittleton.com/event/soap-making-class/
Warning: http_build_query(): Parameter 1 expected to be Array or Object. Incorrect value given in /home/creativ3/public_html/charmedinlittleton.com/wp-includes/Requests/Transport/cURL.php on line 507
After a lot of research, the http_build_query has finally been fixed in the version 2.5.14. We've found that on some very specific installations, the PHP object conversion wouldn't work as expected before calling our API, causing the reported error.