First verify that your email server is working correctly and receiving emails from other addresses. This may be an issue if you're using your own email server or one provided by your website host. There may be some delay from the time you set up your address and the time it starts to successfully receive emails.
Also, remember looking at the spam folder, if you have one. Sometimes Formspree emails may get in there.
If the emails are not in the spam folder, perhaps your email server has returned an invalid response to one of our emails, and was blocked by the email provider Formspree uses. To solve this, please visit
https://formspree.io/unblock/<firstname.lastname@example.org> (replacing it with the email address which your form is targeting).
If you are sure your email is working correctly, and it wasn't blocked by our provider, please submit a support request and we will investigate further.