Unable to set property "ctl.start"

Question

I am using this to configure and start PPTP or L2TP protocol programmatically

L2tpService l2tpService = new L2tpService();

VpnServiceBinder vpnServiceBinder = new VpnServiceBinder();

L2tpProfile l2tpProfile = new L2tpProfile();
l2tpProfile.setSecretEnabled(true);
l2tpProfile.setSecretString("123456");
l2tpProfile.setName("test");

l2tpService.setContext(vpnServiceBinder, l2tpProfile);

Intent intent = new Intent(getApplicationContext(), vpnServiceBinder.getClass());
startService(intent);

After run this code

l2tpService.connect("136.243.133.200", "test", "K@test");

Error:

Unable to set property "ctl.start" to "mtpd": connection failed; errno=13 (Permission denied)

Please help me.