Workflow manager registration problem

When registering Workflow manager in powershell using the following command:

Register-SPWorkflowService –SPSite "http://servername" –WorkflowHostUri "http://workflow.servername.com:12291" –AllowOAuthHttp

I get this error:

Register-SPWorkflowService : Unable to connect to the remote service at
http://workflow.servername.com:12291/SharePoint/. See InnerException for more
details. Client ActivityId : e204c662-f71d-4c94-965d-c0f8596e3f43.
At line:1 char:1
+ Register-SPWorkflowService -SPSite "http://servername" -WorkflowHostUri
"http://wor ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~
    + CategoryInfo          : InvalidData: (Microsoft.Share...WorkflowService:
   RegisterSPWorkflowService) [Register-SPWorkflowService], WorkflowEndpointN
  otFoundException
    + FullyQualifiedErrorId : Microsoft.SharePoint.WorkflowServices.PowerShell
   .RegisterSPWorkflowService

Any ideas?