Paprika uses iOS's built-in Mail settings in order to send email. Please verify that you have an account configured in the Mail app and that you are able to successfully send emails using the Mail app.
If you only have a third-party email app (like Gmail or Outlook) configured, it will not work with Paprika.
This is true even on iOS 14 where a third-party email app can configured as the default email app. The iOS third-party email integration does not currently support including attachments along with the email, so we are still relying on the built-in Mail app in order to send a Paprika recipe attachment with our recipe emails.
If you do have the Mail app configured and don't receive an error message when sending an email from Paprika, please check your Outbox in the Mail app to see if there are any unsent emails there. Usually this means you have an incoming mail account (POP/IMAP) configured but no corresponding outgoing email account (SMTP), or there may be a problem with your SMTP password.