[Plugin: Contact Form With Captcha] Always fails to send email

Whenever I send a message I get the following error – “Can’t send email to Administrator. Please try later”

Have tried with and without specifying an email address in the settings.

Previously used (and reverted back to) “Contact Form Plugin” which works fine

Any ideas?

https://www.ads-software.com/extend/plugins/contact-form-with-captcha/