Where is the "Response Contents" tab when clicked on "Advance" button, we only see "Request Headers" / "Advance settings" / "Variable extractors" / "Recorded request" / "Recorded response"
I'm not sure to understand what you are looking for. Why do you think there's a "response contents" tab?
There's only the tab you mentionned and the server response is stored in the "Recorded response" tab.
The server response can be missing if NeoLoad did not keep the data like for binary content.