Failed to start on boot : Unauthorized: Failed to get tunnel


I have setup a tunnel via CLI on the NexcloudPI. No problems to get it working when I launch the command

cloudflared tunnel run MYTUNNEL

But I would love to have the service running on restart of the PI. However, at boot, I see the message :

ERR failed to serve incoming request error="Unauthorized: Failed to get tunnel"

I am thinking the config.yml is not at the right place, but when lauching manually, the tunnel works.

Any idea ?