Why does the GP Manager not recognise my gradation table?

Error description

It is not possible to use a specific gradation table. Other gradation tables do not have this problem.

Error cause

Probably your gradation table name contains invalid characters. For example it might contain spaces or some special characters.

Solution

Create a new gradation table. Name the gradation table only with letters, numbers and the _ symbol. Afterwards the GP Manager should accept the gradation table.