By default, Flow is not enabled. To enable it, you must select one or both of the Flow permissions on the General tab in the Group properties:

View Flow -  Allows users to view all workflows configured for their tenant. Users with this permission can access the Dashboard and see each workflow, but cannot create, edit, delete, enable, or disable workflows.

Manage Flow - Grants full access to all workflow functionality, including creating, editing, deleting, enabling, and disabling workflows.