Google has recently updated reCAPTCHA to version 3. Contact Form 7 was also recently updated to version 5.1 to take advantage of this. ReCAPTCHA is the item on a form that asks you to click on certain images or asks if you are a robot.
Without reCAPTCHA a lot of people would get a lot of spam emails.
The new reCAPTCHA uses a scoring system, so no need for users to click I am not a robot anymore. Before you update though, be warned there are some issues. Update 5.1.1 attempts to fix some of this.
The creator of Contact Form 7, Takayuki Myoshi, has posted an update regarding the issue.
Some websites, this one included, were seeing an orange border and the following image when submitting our contact form.
Basically the form thinks you are a robot and will not send your message. Myoshi states this is probably due to your theme not properly calling wp_footer(). You can contact whomever made your theme to correct this, or like us turn off reCAPTCHA altogether. Since we are a small website we don’t expect much spam. To turn it off, go to your dashboard / Contact / Integration and remove your keys. That is all you need to do. Contact Form 7 5.1.1 will essentially ignore any [recaptcha] you have on the actual form.
Other people are rolling back their websites to a previous version of Contact Form 7 until this is sorted out better.