Make sure your are setting the VPN config properly.
Here is the sample code.
NEVPNProtocolIPSec *protocalConfigurationIPSec = [[NEVPNProtocolIPSec alloc] init];
protocalConfigurationIPSec.username = @"account";
protocalConfigurationIPSec.passwordReference = passwordReference;
protocalConfigurationIPSec.serverAddress = @"ipaddress";
protocalConfigurationIPSec.authenticationMethod = NEVPNIKEAuthenticationMethodSharedSecret;
protocalConfigurationIPSec.sharedSecretReference = sharedSecretReference;
protocalConfigurationIPSec.localIdentifier = @"userGroup"];
protocalConfigurationIPSec.remoteIdentifier = [serverDict objectForKey:@"userGroup";
**protocalConfigurationIPSec.useExtendedAuthentication = YES;**
protocalConfigurationIPSec.disconnectOnSleep = NO;
manager.protocolConfiguration=protocalConfigurationIPSec;
[manager setOnDemandEnabled:NO];
[manager setLocalizedDescription:@"VPN"];
manager.enabled = true;