I did not receive a confirmation email after creating a Firefox Account, which is now locked. How do I unlock it?

I used my email address to create a Firefox account to synchronise my bookmarks, but a message popped up saying that the confirmation email sent was returned. I tried clicking the link to resend the confirmation email, but still did not receive it (I also checked my spam folder). Now when I try to log into the Firefox account I created, I am told "Sorry. We’ve locked your account. The confirmation email we sent to xxxx@xxxx.com was returned and we’ve locked your account to protect your Firefox data.". I have checked that my email account successfully receives other emails. How can I unlock my new Firefox account?