Function group &1 &2 does not exist

What causes this issue?

Function group with customer Include: customer part <(>&<)>V1& <(>&<)>V2
& <(>&<)>V3& does not exist

System Response

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

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.