Unable to login to vCenter using vijava

Hi,

I am using vijava-5.5-beta and when I try to connect to the vCenter I am getting the below error

java.rmi.RemoteException: VI SDK invoke exception:com.vmware.vim25.InvalidRequest
 at com.vmware.vim25.ws.WSClient.invoke(WSClient.java:122)
 at com.vmware.vim25.ws.VimStub.login(VimStub.java:1483)
 at com.vmware.vim25.mo.SessionManager.login(SessionManager.java:164)
 at com.vmware.vim25.mo.ServiceInstance.<init>(ServiceInstance.java:90)
 at com.vmware.vim25.mo.ServiceInstance.<init>(ServiceInstance.java:69)

vCenter version I tried are vCenter: 5.5.0 Update 2d and VMware vCenter Server 6.0.0

I am using below code to connect to vCenter

String url = "https://{host}/sdk";
ServiceInstance serviceInstance = new ServiceInstance(new URL(url), username, password, true);

Can someone please help me to fix this.

Thanks,

Satish M