I am having a similar problem – upon submit the page refreshes, no success message appears and no email is received. I use the plugin a lot and this is the first time I’ve run into trouble.
The site is: https://byusco.com/contact/location/
Plugins include:
WPeCommerce
WPeCommerce Gold Cart
jQuery Lightbox For Native Galleries
Raw HTML capability
Redirect Parent to First Child
Smart YouTube
Select Widget Context Widget Context
WordPress SEO
Susan