Dear IBN.
Thanks for yourreply, I observe that the settings you provided are under notifications and activity which is different to the settings I provided. Kindly inform them to check under chats and channels and then then Make sure that Viewing chats and channels set to Separate And Make sure that Filters turned off (Kindly see the above reply screenshot).
May I please know if the issue they are experiencing is unable to receive notification?
May I please confirm that you get same situation in both Teams for Desktop and Teams on Web (https://teams.microsoft.com/)?
May I know if you are using windows or Mac device?
Looking forward to your response!
Best regards,
Inema