Costs of production order & cannot be distributed

What causes this issue?

A WBS element or breakpoint with a status that does not allow cost
distribution has been assigned to production order &.

System Response

No cost distribution can be executed for the production order.

How to fix this error?

Check the status of the assigned WBS elements and breakpoints. You can
find these objects using transaction PEG03.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.