DI: Invalid activity type for generic transaction &

What causes this issue?

For the generic transaction, an incorrect value was transferred for the
<DS:DE.BU_AKTYP>activity type</> (AKTYP).

System Response

The generic transaction with the external number &V1& was not
transferred.

How to fix this error?

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.