It looks like you are triggering the workflow by running the Skelta API from your ASPX page in a VS.NET application. You need to verify wether the code has written correctly. Please find some sample below:

Below is sample code for WindowsProvider(Active Directory)

                                                         //ReposrtoryName, WorkflowName

Workflow.NET.Engine.Client objClient = new Client("WindowsRepository", "ContentHandler");

        objClient.Execute("activedirectory::aduser1", "<test>a</test>");

                          //ProviderName:: ActiveDirectoryUser

        objClient.Close();

Below is sample code for SkeltaList provider

                                                              //ReposrtoryName, WorkflowName  

Workflow.NET.Engine.Client objClient = new Client("SkeltaListRepository", "Test");

objClient.Execute("skeltalist::0300012e-3832-4a8c-b627-f5177a649329", "<test>a</test>");

                           //ProviderName, Userid Guid form the SKEUser table from Skelta database    

      objClient.Close();

Below is sample  code for Forms Provider(Xml ResourceHandler)

                                                                   //RepositoryName, WorkflowName

Workflow.NET.Engine.Client objClient = new Engine.Client("FormsRepository", "Test");

        objClient.Execute("sqlprovider::1", "<test>Skelta</test>");

                          //Providername, Userid from resource datbase

objClient.Close();

Below is sample  code for ASP.NET Membership Provider(ASP.NET roles)
                                                                           

                                                       //RepositoryName, WorkflowName 

Workflow.NET.Engine.Client objClient = new Client("MembershipProvider", "Test");

objClient.Execute("membershipprovider::0e004302-22ca-4c94-b7fa-5c96f5a85214","<test>Skelta</test>");

                  //providerName,UserId form asp.net users table(Roles Database)

objClient.Close();

Do let me know if it helps.