FI-SL Planning. No figures can be entered in GP12N

Hello!

The following problem occurs in FI-SL planning: it is necessary to input the plan data in SAP manually, but the column with figures in transaction GP12N is not ready for input.

This operation is made in table group Z*. A ledger is customizeg in this table group. A version for plannig is customized in this ledger. For planning Planning layout is customized and Planner Profile is defined.

It is possible to enter characteristics in GP12N but in Overview screen and in Posting period screen all the fields including columns for Plan amounts are not ready for input.

What can be the problem?

Thank's in advance!