Hi @ネパリ サンデャ
Could you please tell me: Have you encountered this problem recently? Have you tried to use the Teams Web client to see if there is this problem?
Based on our tests, when a user posts in a team with a team mention or mentions an individual, it will show up in the activity.
If you make sure you set the notification to "Show in activities and banners." in the settings and still have this problem. It is recommended that you clear the Teams cache.
In addition, you can report an issue here in the Teams client, which will collect your log files to better solve your problem. If you have any update about this issue, please feel free to post back.
Thank you for your understanding and support.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.