Thanks for reporting this conflict. I’ve requested the author of the plugin send me a copy so that I can troubleshoot this. I’ll update you with my progress.
They sent me a copy of their plugin but things seem to be working for me – since I installed and activated the WooCommerce plugin. That was an essential step. Do you have WooCommerce installed and activated on your site? If so, it may be a configuration issue. Would you mind sending me access details for the affected site via our secure contact form?