I'll include the steps below to create a routine for your reference. Supported devices to control and/or start your routine will appear in step 5 - the list will be different for each user, because the devices shown are the ones you have registered to your Alexa account.
To create a Routine in the Alexa app on your mobile device:
Go to the menu and select Routines.
Select the + icon in the top right corner.
Select When This Happens, and then choose how to trigger the Routine. For sensor routines, select your installed motion or contact sensor.
Select Add action, and then choose which action it completes. To receive a push notification when a motion or contact sensor is triggered,select Send notification.
Under From, select which device controls the routine.
I really hope that helps! If you're still having this issue - make sure your Alexa app is registered to the same account that your Alexa & Smart Home devices are registered to. And please let us know how it goes!