If someone on your project is not receiving email notifications when new comments are made, there's a couple of things that may be the cause.
1. Check your junk mail
It's possible that email filters are sending notification emails into your junk inbox.
2. The user has unsubscribed from email notifications in Marvel or you've disabled comments notifications in the project settings
Anyone receiving email notifications has the opportunity to unsubscribe using the link at the bottom of emails.
It could also be possible that you've disabled comments notifications in the project settings. To enable notifications:
- Head to project settings by opening your project and clicking on the settings icon in the top right-hand corner
- Click on the general tab > comments notifications > toggle on