Getting Error while Submitting Form

Hlw, I recently added cf7 to my website! As I like this plugin so much! I needed some help!

While I am submitting my form! It’s showing “There was an error trying to send your message. Please try again later

How to resolve this!?? And how can I customize all the contact form design! Please help me anyone!!!!

The page I need help with: [log in to see the link]