We have seen in our system that there were multiple confirmation emails sent to your account. Sometimes the verification email can take some minutes to arrive or end up in the spam folder depending on the configuration of the filter of your email account. In case the email is not within your spam then, another possibility is that it might be bounced.
Could you check that you have not blacklisted us as the sender (pix4d or MailChimp, which is our sending channel)?
Additionally please note that you could re-send the confirmation email by login into to your cloud account: cloud.pix4d.com and click RESEND button (see the screenshot below):