Invalid account assignment category; see long text

What causes this issue?

The system should assign a component to an account assignment category.

System Response

The account assignment category is not defined.

How to fix this error?

In Customizing define the account assignment category for service- and
maintenance orders.
In the standard, define the following values for the order category 30:
Account assignment type (general): F
Account assignment type (project): Q
Account assignment type (sales order): E
Sales document project: D

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.