We couldn’t reproduce the problem in any of our testing and production environments.
If the emails are not sent at all, please ensure WordPress mailing functionality works.
Also, Mistape uses abuse checks, so if you’ve sent more than 5 reports in 5 minutes while testing, Mistape would ignore reports from your IP for some time, which could be the reason of emails not being sent.
If Mistape indeed contains an error which is triggered in your environment, webserver’s PHP log could help to diagnose and fix it. If you have access, please send them to us: [email protected].