I have my Google Voice account setup through the Hangouts app for Android, on my un-rooted Galaxy S5 (with the Lollipop OTA).

When I have the application open on my device, and I receive an SMS to my GV number, it appears on screen.

If I don't have the application open, the phone still receives the message, but it does not give me a notification. I know background data is turned on, and it has received the message, because I can turn on airplane mode, then open the app, and see the message is there unread.

"Actual" Hangouts messages notify correctly whether the app is open on-screen or not.

Has anyone ever seen this before?