I had the same problem with my Moto 360 (2015). I have two phones on me: my personal phone, in my pocket, and my work phone at my hip on the same side. My Moto 360 is connected to my personal phone.
I noticed that no notifications got to my Moto 360, until I tried disabling Bluetooth on my work phone. From that point on, it looks like all notifications get to my watch.
Maybe a fluke, maybe a solution if it applies to your situation.
Hope this helps someone.
EDIT - Clarification about which phone the watch is connected to.