Start condition '&1' could not be activated

What causes this issue?

To activate a start condition, the following steps are necessary:
A type linkage between an event of an object type and an event
recipient (workflow) must be created.
A check function module of the workflow system must be entered in the
type linkage.
The type linkage must be activated.
The system has determined that the type linkage needed is already
available and that a user-defined check function module is entered in
this type linkage. Since only one single check function module can be
active, the user-defined check function module in the type linkage must
be replaced by the check function module of the workflow system. Thus
the function defined by the user-defined check function module is no
longer available.

System Response

The user-defined check function module was ignored in the type linkage
The check function module of the workflow system was not entered.
The start condition is not active.

How to fix this error?

If you want to activate the start condition, choose '<ZK>Yes</>' when
asked whether the user-defined check function module is to be replaced.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.