Using wired headphones with Node 2i and NAD preamp/amp

Hello,
I am using the following configuration
Media player Bluesound Node 2i connected with RCA cables to an integrated amplifier NAD C326BEE used as a preamplifier, itself connected via Pre-Out to a power amplifier NAD C275BEE, connected to the loudspeakers.

I recently bought wired headphones (Meze Classics 99) that I connected to the headphones connector on the front panel of the C326BEE. It is supposed to cut the sound of the loudspeakers but it does not and there is no sound in the headphones.

The Node 2i is set with fixed volume as I am using the C326BEE to control volume.

When connecting the headphones to the Node 2i headphone connector, sound works correctly in the headphones. But I expect to have a better sound quality by using the NAD326BEE directly with headphones.
If I switch off the power amplifier and only keep the C326BEE on, there is still no sound.

Can you please help me and inform how to set up ?

Thanks in advance for your advices
Marc