Diagnosis
Structure indicator &V1& is supposed to be used for formatting theappropriation request number.
According to Customizing settings, structure indicator &V1& can only beused for appropriation requests of appropriation request type &V2&.(See Customizing: Coding Masks for Appropriation Requests)

System Response
The system does not allow the structure indicator to be used.

Procedure
Use a different structure indicator.
Check your Customizing settings for a valid structure indicator:Limiting Structure Indicator