I've installed and configured Workflow Manager 1.0 +CU3 in a standalone SharePoint 2013 farm patched to SP2 Feb2015CU.
In order to eliminate as many issues as possible, I've created a very simple SharePoint Designer workflow with 1 stage. The only action it performs is logging a message to the workflow history list.
I have a 2013 workflow associated to a list and allow it to be manually started. When I manually start it, it stays in a 'Starting' state forever.
I see the following exception being logged immediately after application authentication when I turn on verbose ULS logging:
Workflow instance 0d39e99d-b7a3-4827-af42-2c39b4c0461a is in retry state but GetRetryMessage threw exception: System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary. at System.Collections.Generic.Dictionary`2.get_Item(TKey key) at Microsoft.SharePoint.WorkflowServices.FabricWorkflowInstanceProvider.GetRetryMessage(WorkflowInstance instance) at Microsoft.SharePoint.WorkflowServices.FabricWorkflowInstanceProvider.GetInstance(Guid instanceId)
There were no errors during the installation/configuration of either Service Bus or Workflow Manager. I have followed the troubleshooting guides and the only thing I can see is I do get an untrusted certificate error when I browse to the :12290 address for the workflowhosturi although that is NOT the uri I used when registering the service.
Note: when I performed the Register-SPWorkflowService cmdlet this is what I entered: