Hi,
I confirm all my datarefs according the manual are disabled (I checked each of them).
But I found the reason of my problem. I installed X-IVAP plugin (to connect on IVAO network). And with X-IVAP plugin installed, the GTN don't work, otherwise without X-IVAP plugin, GTN work fine !
In attachment, 2 screenshots with datarefs window visible (and X-IVAP installed...GTN don't work)