Check the health of the database using the loopback IP and port 2379 ( LAB 4-1 )

hi dears,
i want to start LAB 4-1 but in the first step i faced error when use this command >>>

student@master:˜$ kubectl -n kube-system exec -it etcd-master -- sh \
-c "ETCDCTL_API=3 \
ETCDCTL_CACERT=/etc/kubernetes/pki/etcd/ca.crt \
ETCDCTL_CERT=/etc/kubernetes/pki/etcd/server.crt \
ETCDCTL_KEY=/etc/kubernetes/pki/etcd/server.key \
etcdctl endpoint health"

ERROR >>
sh: : command not found
sh: line 1: : command not found
sh: line 2: : command not found
Error: KeyFile and CertFile must both be present[key: /etc/kubernetes/pki/etcd/server.key, cert: ]
command terminated with exit code 128

when i Log into the etcd container and check this command >> sh-5.0# etdctl endpoint health

Error >> {"level":"warn","ts":"2021-03-08T07:01:37.934Z","caller":"clientv3/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"endpoint://client-6568ae95-1d70-4822-8f7f-f8929c7b5b91/127.0.0.1:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = latest balancer error: all SubConns are in TransientFailure, latest connection error: connection closed"}
127.0.0.1:2379 is unhealthy: failed to commit proposal: context deadline exceeded
Error: unhealthy cluster

what is this error and how could i solve it ??
i do everything from first and make master and worker node again but i got this error again.