Ubuntu 18 kubernates don't go up after reboot

Hi I have installed kubernates trought kubeadm init, only one node, with nginx and metalllib installed
The server rebooted and now kubernates pods stays on error
and the pods show this error:

 Warning  FailedSync              37m                     kubelet, master-node  error determining status: rpc error: code = Unknown desc = Error: No such container: b6e5a7e6c064c41a1591705caf7d12f0b3dd2191bad8dab676ccc7f13d7388dc
  Warning  FailedCreatePodSandBox  7m11s (x7664 over 42h)  kubelet, master-node  (combined from similar events): Failed to create pod sandbox: rpc error: code = Unknown desc = failed to set up sandbox container "7b6d177375197fc39a032de97d81e2252e87a4d1bf307ed53b21e5778c7e8159" network for pod "portalapi-dep-c8845948b-7sf2w": networkPlugin cni failed to set up pod "portalapi-dep-c8845948b-7sf2w_default" network: open /run/flannel/subnet.env: no such file or directory
  Normal   SandboxChanged          2m20s (x7688 over 42h)  kubelet, master-node  Pod sandbox changed, it will be killed and re-created.

Cluster information:

Kubernetes version: 1.18.6
Cloud being used: bare-metal
Installation method: kubeadm init + nginx controller + metallib
Host OS: Ubuntu 18.04
CNI and version: ?
CRI and version: ?