Structure indicator &1 is blocked for new approp. requests - change

What causes this issue?

You want to use structure indicator &V1& for the formatting of the
appropriation request number.
However, according to its Customizing settings, structure indicator
&V1& is blocked for new appropriation requests. Therefore, you cannot
use it.

System Response

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

How to fix this error?

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

Error message extract from SAP system. Copyright SAP SE.