@mitu Thanks! I found the real issue why it was not detecting after some research. Three points to note:

My Pandora 3d's top USB port must be used to connect with Raspberry pi4. Pandora must be powered ON to detect the controller. Once Pandora connects, Pandora goes to "Controller" mode(a full screen message shows up) and disables its controller on Pandora but activates on raspberry pi.

Now, I am using both systems on my arcade cabinet side by side using an HDMI switcher.

Hopefully these would help other people. :)