Per the issue below, you have to request ON/OFF commands slightly differently. This is probably a limitation on the Alexa side due to the overlapping with the PowerController/ToggleController interfaces.
“Alexa, stell das Licht Garage auf Aus”
Simulator Screenshot
Event Logs
2019-12-28 18:23:42.596 [ome.event.ItemCommandEvent] - Item 'SWI10_Scene' received command 1
2019-12-28 18:23:42.597 [vent.ItemStateChangedEvent] - SWI10_Scene changed from 0 to 1
2019-12-28 18:23:47.109 [ome.event.ItemCommandEvent] - Item 'SWI10_Scene' received command 2
2019-12-28 18:23:47.110 [vent.ItemStateChangedEvent] - SWI10_Scene changed from 1 to 2
2019-12-28 18:23:56.988 [ome.event.ItemCommandEvent] - Item 'SWI10_Scene' received command 0
2019-12-28 18:23:56.989 [vent.ItemStateChangedEvent] - SWI10_Scene changed from 2 to 0