problem
It can be found that it is a path problem
solve
ExecStart=/usr/bin/dockerd --tlsverify --tlscacert=/root/tls/ca.pem --tlscert=/root/tls/server-cert.pem --tlskey=/root/tls/server-key.pem -H tcp://0.0.0.0:2376 -H unix:///var/run/docker.so
Restart again
systemctl daemon-reload
systemctl restart docker