Try using a normal viewportframe - what is the result?
Are you sure you are creating the camera instance? All camera instances are destroyed on game start.
Did you set the viewportframe’s CurrentCamera value to the camera?
Are the positions right? Try using a viewportframe editor plugin to set the camera’s CFrame.
Is there anything on top of the viewportframe that could be blocking your view of it?
Are you sure you have parented the object you want to display to the viewport frame?
Could you send us the section of the Explorer Window that shows us the viewport frame, its parents and its children too? Its properties would also be useful!