# Machine Workflow Exception Value cannot be null **URL:** \ **Category:** Flow Classic\ **Tags:** portal\ **Created:** [March 12, 2024, 2:07pm UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643 "2024-03-12T14:07:24Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![nasiralim](https://avatars.discourse-cdn.com/v4/letter/n/7C9FD7/32.png) [@nasiralim](https://forum.novacura.com/u/nasiralim)\ **Post date:** [March 12, 2024, 2:07pm UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643/1 "2024-03-12T14:07:24Z")
When the top filters load properly there’s an issue in child portlet that listens to filters on row selected. deleted the portlet and re imported it but no luck. ![Screenshot 2024-03-12 at 7.33.57 PM](https://europe1.discourse-cdn.com/flex013/uploads/novacuratalk/original/1X/0e3cffb10fac3868aab1f0995a372c8230b57d18.jpeg) ---
**Author:** ![Alluse](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.novacura.com/alluse/32/1013_2.png) [@Alluse](https://forum.novacura.com/u/Alluse)\ **Post date:** [March 13, 2024, 10:08am UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643/2 "2024-03-13T10:08:33Z")
Hi, It probably because the child portlet is configured in a way so it expects a certain data structure, and when you apply the filter/listener command the results is null. What is the data source of the child portlet and what filter do you apply? ---
**Author:** ![nasiralim](https://avatars.discourse-cdn.com/v4/letter/n/7C9FD7/32.png) [@nasiralim](https://forum.novacura.com/u/nasiralim)\ **Post date:** [March 13, 2024, 10:30am UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643/3 "2024-03-13T10:30:03Z")
this is working normally in other environments. with same setup. Child has a datasource from workflow and listens to search portlets on row selected. ---
**Author:** ![Alluse](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.novacura.com/alluse/32/1013_2.png) [@Alluse](https://forum.novacura.com/u/Alluse)\ **Post date:** [March 13, 2024, 10:42am UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643/4 "2024-03-13T10:42:10Z")
I see, but the data might be different and consequently the data provided for the portlet. ---
**Author:** ![nasiralim](https://avatars.discourse-cdn.com/v4/letter/n/7C9FD7/32.png) [@nasiralim](https://forum.novacura.com/u/nasiralim)\ **Post date:** [March 13, 2024, 11:33am UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643/5 "2024-03-13T11:33:53Z")
Checked the query that returns values from parent porlet, it is sending same result in both environments. ---
**Author:** ![Alluse](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.novacura.com/alluse/32/1013_2.png) [@Alluse](https://forum.novacura.com/u/Alluse)\ **Post date:** [March 13, 2024, 12:00pm UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643/6 "2024-03-13T12:00:23Z")
Are you using a workflow as datasource for the portlet? if not, change to that. It’s more flexible and easier to debug. ---
**Author:** ![nasiralim](https://avatars.discourse-cdn.com/v4/letter/n/7C9FD7/32.png) [@nasiralim](https://forum.novacura.com/u/nasiralim)\ **Post date:** [March 13, 2024, 12:19pm UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643/7 "2024-03-13T12:19:01Z")
yes I am using a workflow as data source. ---
**Author:** ![nasiralim](https://avatars.discourse-cdn.com/v4/letter/n/7C9FD7/32.png) [@nasiralim](https://forum.novacura.com/u/nasiralim)\ **Post date:** [March 13, 2024, 12:50pm UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643/8 "2024-03-13T12:50:26Z")
2024-03-13 13:25:48,818 - Portal exception NovaCura.Flow.Client.Web.ErrorHandling.Exceptions.PortalCallException: MachineWorkflowExecution exception. Value cannot be null. Parameter name: key (log key: lGE\_ydh7EUq-ckOYzYFGYg) at NovaCura.Portal.Services.ApiCall.ResponseValidator.Check[T](FlowServerResponse`1 response) at NovaCura.Portal.Services.DataSource.DataSourceService.GetWorkflowData(Guid sittingKey, SharedDataSourceWorkflowRequest dataSourceRequest) at NovaCura.Portal.Services.Workflow.WorkflowExecutors.PaginableWorkflowExecutor.Execute(PaginableDataSourceExecutionDto workflowExecutionDto) at NovaCura.Portal.Services.Execution.PaginableWorkflowExecutionService.Execute(PaginableDataSourceExecutionDto paginableDataSourceExecutionDto) at NovaCura.Portal.Services.Execution.PaginableExecutionService.Execute(PaginableDataSourceExecutionDto dataSourceExecutionDto) at NovaCura.Portal.PortletPlugin.Table.Services.TablePaginationStackService.Post(TableRequest request) at lambda_method(Closure , Object , Object ) at NServiceKit.ServiceHost.ServiceRunner`1.Execute(IRequestContext requestContext, Object instance, TRequest request) Error log from server ---
**Author:** ![Alluse](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.novacura.com/alluse/32/1013_2.png) [@Alluse](https://forum.novacura.com/u/Alluse)\ **Post date:** [March 13, 2024, 2:53pm UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643/9 "2024-03-13T14:53:17Z")
It seams that your workflow throws an exception. I would start debugging the machine workflow by sending the payload it receives from the portal from e.g Postman and try to re produce the error. Alternatively you can run the Flow in testbench with the same input; declare values at the start and run the Flow in the test bench. ---
**Author:** ![nasiralim](https://avatars.discourse-cdn.com/v4/letter/n/7C9FD7/32.png) [@nasiralim](https://forum.novacura.com/u/nasiralim)\ **Post date:** [March 13, 2024, 3:36pm UTC](https://forum.novacura.com/t/machine-workflow-exception-value-cannot-be-null/643/10 "2024-03-13T15:36:41Z")
Thanks it was issue with one of the connector in a step of work flow. Appreciate your help.