This issue could be caused by the web browser you are using, as each web browser is different one from another. Do any of the following:
1. Check if cookies are enabled in your web browser (enable them if otherwise).
2. Delete your existing cookies and type in the verification code again. Next, submit the form.
Follow this step if you are the owner of the web form or survey:
Go to your CAPTCHA protection settings in Settings → Security or Editor and change it to Daily Changed CAPTCHA. You could always remove CAPTCHA completely if you want to keep cookies. But you may still protect your web form or survey from spammers by limiting submissions from the same IP.
Our customer support specialists are more than willing to help you. Just leave them a message at email@example.com or send us an email in the contact form below whenever you require assistance.