update - more than one user notice this problem ==> Maybe this is a system bug/issue.
In general cases:
- Email software: Check under your email account
Spam section.
- Designer: Create a new “test” form (Maybe you change the form setting).
- Setting: Check if the emails are correct (Under Project settings > Forms tab).
- Custom code: Your site use any custom code for forms? (Zapier/mailchimp and so on).