I also have a Harmony remote and cannot get Ring to show via an echo dot command until I ‘wake’ the Fire TV remote with any press, then it works without fail.
It is so irritating that you need to do this, particulary when I have an automation that shows the camera feed on my TV when my doorbell detects motion (a Sonos speaker ask my dot to ‘show the front door’), it works flawlessly, but the camera feed never shows unless I’ve ‘woken up’ the Fire TV remote first!