K3s-agent doesn't sent its metrics

here comes my (simple) architecture:

  • 1 server runs k3s-server;
  • 1 server hosts Rancher;
  • 2 mini pcs run k3s-agent.

I can use Rancher to deploy pods on the edge computers.
But their metrics (CPU/MEMORY) are not sent, although the k3s-server does.

sudo kubectl top nodes

NAME          CPU(cores)   CPU%        MEMORY(bytes)   MEMORY%     
server1        480m         6%          2207Mi          27%         
edge2         <unknown>    <unknown>   <unknown>       <unknown>   
edge1         <unknown>    <unknown>   <unknown>       <unknown>

I have used this simple given command to install k3s-agent:

curl -sfL https://get.k3s.io | K3S_URL=https://mydomain.com:443 K3S_TOKEN=

What should I do to fix this metrics issue?