Internal: event &1 for object type &2 cannot be triggered

What causes this issue?

Only the following required parameters are currently filled:
Object category: &v2&
Object key: &v3&
Event: &v1&

System Response

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

&sys_admin&
Please make sure that all the required parameters are filled in variant
&v4&.

Error message extract from SAP system. Copyright SAP SE.