Diagnosis
You want to use structure indicator &V1& for the formatting of theappropriation request number.
However, according to its Customizing settings, structure indicatorV1 is blocked for new appropriation requests. therefore, you cannotuse it.

System Response
The system does not allow the use of the structure indicator.

Procedure
Use a different structure indicator. Use the input help to see possiblecoding masks.
Check your Customizing settings.