TCG11: cannot find name for class &1 in value assignment type &2

What causes this issue?

The system was unable to find a class name for the assigned class &V1&,
which is assigned to the value assignment type &V2&. This indicates that
the class assigned in TCG11 does not (yet) exist in the system.

System Response

The (new) field in table TCG11 remains blank.

How to fix this error?

Ensure that you have converted and activated the table with the class
definitions (KLAH).
Should an error occur during the conversion program, there is a risk of
data inconsistencies. In this case, you cannot use Product Safety and
Stewardship. Lock the relevant transactions (all transactions starting
with CG) until the problem has been solved.

Error message extract from SAP system. Copyright SAP SE.