Submit button not working correctly

Hi, hope you can help me. I have been using this plugin successfully for 2 years on this website https://www.sungreektaverna.co.uk, For some reason the button & reply message for user are not working correctly, no reply message and the button does not depress. I have recently changed servers where I need to use an SMTP plugin to allow mail scripts. I would really appreciate if you could take a look at this for me. Kind regards

https://www.ads-software.com/plugins/responsive-contact-form/