SCE mode not active - maintenance of tasks and events not allowed

What causes this issue?

Tasks and events can only be used for the Sales Configurator Engine
(SCE). You cannot work with tasks and events in the R/3 configurator.

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?

You can only download existing configuration models to the SCE. You
cannot use the SCE functionality to create new configuration models, so
you cannot work with tasks and events.

Error message extract from SAP system. Copyright SAP SE.