When a guest receives a personalized invite from one of your events and clicks the 'Confirm' button, they are sent to a confirmation page which displays in their web browser. Before this confirmation page can load and register your guest, a Google reCaptcha security check is performed. This process makes sure that a real person is clicking the Accept link in your email, and not an automated program or 'bot'. Without this security step, your event could be flooded with erroneous confirms and declines.
Very occasionally, a guest's company's browser security settings or firewall will not allow this security check to take place and your guest can be kept in a security check loop without getting through to the Confirmation Page.
If you receive a report of this, you can forward the affected guest the link to your event's public Register Page and ask them to copy and paste it directly into the web address bar of their browser.