In order for an Occurrence to utilise Tasks, it must first be part of a Programme that is configured to allow tasks.
In order to toggle this option, start by opening the Configuration Manager by choosing Manage > Configuration from the menu, or click theicon on the toolbar or from the Dashboard.
Locate the heading for Programmes and either choose to Add a new Programme (if required), or instead expand the heading to Edit an existing Programme:
This will display the Programme Wizard:
Within this window, ensure that the Allow occurrence to have tasks checkbox is enabled to allow any occurrences within this programme to have access to Task management tools.