Using classic Outlook for Windows in educational settings
For Windows 11 Enterprise Outlook I also have this issue when I using my outlook for the very first time. You can do this to view your reply and forward messages.
In Outlook Menu on top click on View > gear icon Current View > Show as conversations > select all mail box
Then click on the View > gear icon Current View > Conversations Settings > check Always Expend Selected Conversation
Hope this help someone.