It's a limitation with Alexa/Amazon. They do not allow door locks or garage doors to be tied to Alexa routines, and it even says as much in the ST Alexa SmartApp. Scenes and routines with unsupported devices will not work with Alexa. Your way around it would be to create a virtual momentary button or switch to trigger with Alexa, and then to have your scene or routine activate based on the status of that button or switch.