Email doesn’t send – it just hangs

I installed this plugin and it seems quite simple, and expected it to work quickly. I copied the correct code into the contact form 7 and the captcha displays, but after clicking on that to check the box, and trying to click “Send” to send the email, the form is showing rotating circles and never sends the email. When I remove the captcha statement from the form, it works fine and sends the email immediately. What can I do to correct this? Thanks!