Unit costing is not allowed in plan integrated objects

What causes this issue?

Unit costings are only possible in orders/WBS elements where plan
integration is not active.

System Response

Choose the paths shown to check whether the plan integration indicator
is set:

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

in an order type
(Controlling -> Overhead cost controlling -> Overhead cost orders ->
Order master data -> Define order types
in a project profile
(Project System -> Project planning -> Costs -> Basic settings ->
Activate plan integration in the project profile.

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.