Symptoms

I can manually start a workflow but it won't start when "item created" option has been chosen and deployed using K2 for SharePoint. This occurs on all libraries in this environment. After finding some related articles in the support portal, they aren't relevant to our environment.
 

Diagnoses

We noticed the following error in application event log:
7008 The following error occurred while executing policy for CustomEventInstanceID: 230 : Unauthorized Assembly.
AND
7498 An error has occurred: System.Exception: Unauthorized Assembly
at SourceCode.EventBus.Server.EventQueueProcessing.ExecuteAssembly(Int32 CustomEventInstanceID, Int32 CustomEventID, ResolvedPolicyMapping resolvedPolicyMapping, Boolean isConditional, Int32 eventTypeID)
at SourceCode.EventBus.Server.EventQueueProcessing.ProcessEvent(Int32 ID)
 

Resolution

After reviewing K2HostServer.exe.config, we notice that the following entry is missing:
<assembly displayname="SharePoint15ProcessStarter" fullname="C:Program Files (x86)K2 blackpearlHost ServerBinSourceCode.EventBus.SharePoint15.ProcessStarter.dll" />
Adding the missing entry and restart K2 service resolved the issue.