Error message shown with no box

Hello,

My contact forms have stopped working since updating to wordpress 4.8. I’ve turned off all plugins and tried installing a later version of contact form 7.

I receive the following error, but it doesnt have a box around it.

“Failed to send your message. Please try later or contact the administrator by another method.”

My website is https://showboat.net.au/contact-showboat-cruises/

Has anyone had a similar problem?
Thanks for your help.