Sharepoint 2013 Custom ADFS Login page Error

Hello

I have configured SharePoint to work with ADFS and all was great. However when I created a custom login page and tried to manually login the user using the token retrieved from ADFS as shown below:

 EstablishSessionWithToken(realToken, Microsoft.SharePoint.IdentityModel.SPSessionTokenWriteType.WriteDefaultCookie);

I receive the following error:

System.NotSupportedException: The private key is not present in the X.509 certificate.

[NotSupportedException: The private key is not present in the X.509 certificate.]
   System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg) +14579646
   System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type) +622
   Microsoft.IdentityModel.Protocols.WSTrust.IWSTrustContract.Issue(Message message) +0
   Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.Issue(RequestSecurityToken rst, RequestSecurityTokenResponse& rstr) +69
   Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.Issue(RequestSecurityToken rst) +37
   Microsoft.SharePoint.SPSecurityContext.SecurityTokenForContext(Uri context, Boolean bearerToken, SecurityToken onBehalfOf, SecurityToken actAs, SecurityToken delegateTo, SPRequestSecurityTokenProperties properties) +1429
   Microsoft.SharePoint.SPSecurityContext.SecurityTokenForOnBehalfOfContext(Uri context, SecurityToken onBehalfOf) +72
   Microsoft.SharePoint.IdentityModel.SPFederationAuthenticationModule.ExchangeArgumentTrustedThirdPartySessionSecurityTokenForLocalToken(SecurityToken thirdPartyToken, SessionSecurityTokenCreatedEventArgs arguments) +2622
   Microsoft.SharePoint.IdentityModel.SPFederationAuthenticationModule.OnSessionSecurityTokenCreated(SessionSecurityTokenCreatedEventArgs eventArgs) +662
   Microsoft.SharePoint.IdentityModel.SPFederationAuthenticationModule.SetPrincipalAndWriteSessionTokenWithOptions(SecurityToken securityToken, SPSessionTokenWriteType writeOperationType) +864
   Microsoft.SharePoint.Utilities.SecurityContext.RunAsProcess(CodeToRunElevated secureCode) +221
   PortalPOC.Layouts.PortalPOC.Login.Login.Page_Load(Object sender, EventArgs e) +520
   Microsoft.SharePoint.WebControls.UnsecuredLayoutsPageBase.OnLoad(EventArgs e) +300
   System.Web.UI.Control.LoadRecursive() +95
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2936

Thank you in advance!