The motion snooze isn't working for me either. I have a contractor doing some work & Alexa keeps telling me every time he walks across the driveway. I see from a quick search this has been an issue for a long time.
This is annoying to me, and annoying to the people doing the work, as it must make them feel like their every move is being watched.
I've tried the snooze from the Android phone app, and from the iPad app, and neither had any effect on the incessant notifications.