Ok, the problem is traced.
It seems that you are testing this plugin on your localhost where SMTP settings are not configured, due to which enquiry form is facing some problem while sending an email and hence errors are occurring.
Please configure SMTP settings for your localhost and then test. You may refer this link – https://stackoverflow.com/questions/600725/how-to-configure-wamp-localhost-to-send-email-using-gmail
The best way would be to test the plugin on a live site(where SMTP settings have already configured) instead of testing it on localhost.
One more thing: Since, you are using WAMP server, it is showing various notices/warnings otherwise it shows a message ‘Unfortunately, a server issue prevented delivery of your message’ when an email sending goes fail. That means there is some problem with server side configuration.
Hope, this suggestion will help.
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