Diagnosis
When you define a derived depreciation area, it should be based on atleast two real depreciation areas, since it is only possible to add orsubtract when at least two depreciation areas are involved.
However, depreciation area &v2& in chart of depreciation &v1& is basedon only one real depreciation area.

Procedure
Check the definition of depreciation area &v2& in chart of depreciationV1.