Cubase Lowering the volume on M-Track Duo Output

I’ve just purchased an M-Audio M-Track Duo so that my team and I could assess our work through some bookshelf speakers(M-Audio BX5 D3 Powered Studio Reference Monitors). We’ve been using Cubase LE to edit tracks for around 3 years now, but once we switched output from the speakers to the headphones ,playback volume of our tracks drastically decreased. This was the same for both the M-Track Duo headphone jack, and the onboard jack for our laptop. All other applications on our laptop were not affected by this, it was limited to Cubase LE while on the M-Audio driver in the Studio Setup.
We’ve tried different ways to troubleshoot, from finding updated drivers, re-installing them, checking the M-Track Duo iteself for any issues with the dials. But it seems to be Cubase related at this point.
Has anyone experienced a similar issue or has any info to help us out. It would be really appreciated.

As far as I can tell, and please correct me if I’m wrong, this interface is a 2in/2out interface. Meaning that you can’t route different audio to the Main outputs and the Headphone outputs.

Can you explain what you mean by “switched”? My understanding is that audio is sent in parallel to both the Mains and Headphone outputs.

Thanks for taking the time to help me out. Yes it is the 2in/2out interface. When I say “switched” I mean that we physically unplugged the speakers and swapped over to headphones, not that say, we switched the Output from USB to Direct Stereo or Mono. The speakers work extremely well for our purposes. Just that the headphones through Cubase specifically, are very soft.

If I understand your interface correctly, there is no option to route audio to either the Main outputs or the Headphones outputs. If that is true, the application on your computer sending audio to your interface doesn’t have knowledge about what physical outputs is being used.

I would try this.
Find an audio file and play it with a media player. (I would choose VLC player.) Make sure any volume or gain controls in the player is set to 0dB. Including any volume controls the OS might impose.
Then take the same audio file and place it on an audio track in Cubase. Again, make sure all volume faders are set to 0dB as well as Control Room volume, if you’re using the Control Room.