The system checks for unread activity in your workspace every 15 minutes. Some of the reasons that you haven't received an email notification could be:
15 minutes haven't passed yet.
You have already accessed the ticket on your Shake dashboard after it arrived, in which case the system won't notify you via email too.
The email ended up in your Promotions or Spam email folder, check them out.
If none of the above helps you, please let us know whether by chatting to us using the bubble in the bottom right corner, or emailing us at firstname.lastname@example.org 📬