when instantiating MessagingStyleInformation, the person object needs to be the sender of the potential reply. see https://developer.android.com/reference/android/app/Notification.MessagingStyle#MessagingStyle(android.app.Person)
in your scenario, you'd have to go from
MessagingStyleInformation(
person,
conversationTitle: isGroup ? notifData.receiverProfile.name : notifData.senderUser.name,
groupConversation: true,
messages: notifMsgs
)
to something like
MessagingStyleInformation(
Person(
key: auth.currentUser!.uid,
name: auth.currentUser!.name, // or name: 'You'
)
conversationTitle: isGroup ? notifData.receiverProfile.name : notifData.senderUser.name,
groupConversation: true,
messages: notifMsgs
)