#ProjectServer 2010 Resource assignment behaviour when adding another resource to an existing task with a Generic Resource #PS2010 #MSProject #EPM

Recently an issue came up at a client where they would get “Unknown Resource” error pop up when adding a second resource to a task using the Resources Tab on the Task Information dialog box in Project Professional.

It is probably easier to explain the issue by showing the repro steps below.

Firstly create a new project plan in Project Professional with one task, add a generic resource to the team then assign the generic resource to the task:


The user that created this plan is Support Service, you can see below this user is the assignment owner:


Save and publish this project plan as normal. Then another user, in this case using my own account, opens the project and wants to add another resource to Task1. This user builds the team and adds the 2nd resource, in this case UserA:


Now the 2nd resource is on the project team this user tries to add UserA to Task1 using the Resources Tab on the Task Information dialog box:


Click OK then the user will see the following error and the resource is not added to the task:

Unknown Resource


As the error pops up after adding UserA it is not obvious why this occurs. The reason this occurs is because Support Service is not part of the project team and I’m not the Project Owner. If I opened the project plan as Support Service and added UserA I would not see this issue.

There are several ways around this for the example above, these are detailed below.

  • Add Support Service to the project team
  • When on the Resources tab, update the Assignment Owner for the Generic Resource to Project Owner then add the 2nd resource:


  • Add the second resource via the Resource Names column instead of using the Resources tab on the Task Information dialog box:


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