Assigned usage has been deactivated

What causes this issue?

You can specify for each value assignment type whether its value
assignments are activated after you changed them.
In the current value assignment type, changed values are automatically
deactivated.

System Response

The system deactivated all usages existing for the current value
assignments.

How to fix this error?

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.