functionId &1: Prefix 'ES:' required

What causes this issue?

Ranking functions defined in Enterprise Search are addressed by the
prefix 'ES:'; like 'ES:ES_SESSION_USER'.
As there is currently no other source of ranking functions, this prefix
is mandatory.

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?

Add the prefix 'ES:' to the Enterprise Search ranking function.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.