Hey there,
Vishaal here with Trello Team—thanks for reaching out
To receive notifications of certain actions on a card, you must be watching the card (https://support.atlassian.com/trello/docs/watching-cards-lists-and-boards/), list or board where the card is or you have to be a member of the card in question.
To test this, try the following steps:
1. Go to https://trello.com/your/account and make sure your email notifications are sent "instantly".
2. Create a new Trello board.
3. Create a new card called "test card"
4. Become a member by clicking "Join" or start watching the card by clicking the "Watch" button when the card is open.
5. Invite another user to the created board.
6. Close Trello.
7. Ask the other user to comment on the test card.
You should see a notification in your email about that comment within the next 15 minutes. Once you receive the email notification, you can check Trello, where you should see a notification in the notification section about the comment.
For mobile, there is another set of notification controls that you can use. This will allow you to control what types of notifications you want to receive on your mobile phone: https://support.atlassian.com/trello/docs/mobile-push-notification-settings-for-trello/
If you don't see this behavior, please provide us with the following information so we can further investigate the issue:
1. A screenshot of the card in question (from which you do not receive notifications).
2. A screenshot of the top of the notifications page (click the bell icon in the top right to view this page)
Once we have that, we'll be happy to take another look at it!
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