3381350 - Sytsem Failed to Asisgn a Processor to the Notification - Purchase Order ABC with Reference to Project XYZ was created or updated

You have done the changes to the purchase order that references to the project which is created or updated. And hence the notification triggered to inform the project manager.

SAP Business ByDesign

1. Go to Application and User Management work center
2. Go to Business Task Management view
3. Select Unassigned Tasks
4. You can see the notification type Purchase Order ABC with Reference to Project XYZ was created or updated

The system automatically assigns this notification to the project manager of the project that is referenced by the purchase order. System did not assign the notification because the project manager have no validity.

You can extend the validity of the project manager and then try to acknowledge the notification. 
The user can view this notification in the Home work center -> Work view -> Inbox sub view.

In the Inbox sub view, select the notification
From the Actions menu, choose Acknowledge
The notification is removed from your Inbox

Note: For the unassigned notification, you can assign the notification manually from the below steps;

1. Go to Application and User Management work center
2. Go to Business Task Management view
3. Select Actions -> Assign Item
4. In the new screen, assign the notification to the valid business user
5. Select ok

You can refer to the SAP Help document for further information on this:

Notification - Purchase Order with Reference to Project was Created or Updated | SAP Help Portal 

Notifications not assigned to the processor, purchase order is created or updated in the project, unassigned notifications  , KBA , AP-PRO , Project Processing , Problem