Keyserver failure

Good afternoon,

I try to install LinuxCNC on my Asus VC66 (64 bit)

I installed Debian 9 64-bit; Gnome 3.22.2 and I'm struggling with linuxCNC
I followed all these steps:
linuxcnc.org/docs/2.7/html/getting-start...th_preempt_rt_kernel

But when I enter this command:
sudo apt-key adv --keyserver hkp://keys.gnupg.net --recv-key 3cb9fd148f374fef

I always receive the same message: pgp: keyserver receive failed: Server indicated a failure.

I don't manage to bypass this with sudo apt-get --allow-unauthenticated update
I also try to add [trusted=yes] such as:

deb [trusted=yes] linuxcnc.org/ wheezy 2.7-uspace base

but still the same error

Do you have any idea?
This is too soon to have an error on the long way to get the mill working

Thank you

i resolved the issue with addind ":80" after the key url

let struggle with linuxcnc-uspace erreors now

I think I have generally not bothered with the key, and things seem to work regardless.