Hi Toby,
Thanks for your reply, but I feel stupid, I was using the veyon-ctl command to reset config within a regular Command Prompt window ... (I still don't get why I need admin privilege when I'm already admin). Opening a Command Prompt as Administrator was what I've miss earlier to reset the config and push the new one.
All your suggestion were done it was Windows that trick me (again)
Sorry for the useless noise.
and thanks again for your reply.