GRE tunnel to home network

I’m trying to setup a GRE tunnel from a VPS from Hetzner to my home server. My home server is exposed via DMZ through an Asus RT-AC68U router. I’m using this tutorial: https://community.hetzner.com/tutorials/linux-setup-gre-tunnel

I’m stuck at the ping part: my home server can’t ping to 10.0.0.1 and my VPS can’t ping to 10.0.0.2.

Is this even possible? If so, what should I do to fix it?