Contact form 7 causing PHP Fatal error

Hi, I was seeing a 500 internal sever error on my site and after contacting my hosting company, they determined it was due to Contact Form 7. With the plugin disabled, the site is live again. Below is the error it was giving from my site’s error log. I was using version 4.6 of the plugin, and the site was up without issue as early as this morning with no changes made today. Any ideas on what is causing this? Thanks in advance for your help!

Error:

[09-Dec-2016 00:23:39 UTC] PHP Fatal error: Call to undefined function wpcf7_ajax_loader() in /home2/drinkwe3/public_html/wp-content/plugins/contact-form-7/includes/controller.php on line 168