If you are using a Wordpress site, and are using Contact Form 7 (CF7) plugin, and you have an issue where nothing appears to happen when you click on the submit / send button, then check your page optimisation settings.
In my instance, I was using Litespeed Cache plugin, and needed to have the setting Defer Javascript (Javascript Deferred) set to OFF, and then the submission of the form worked fine.
So having javascript deferred to ON was causing issue with Contact Form 7 form submission.
Hope this saves you time!
