Hi:
Google Hangouts works entirely independently of the Google Chat protocol used with OBi devices. Hangouts will ring on any/all devices running the software, as long as you're logged into your Google account on those devices.
Chat, on the other hand, is more limited. If you're logged onto your Google/Gmail/GV account on your PC, and that PC was the most recent client to communicate with the Chat server, your OBi 1x0 device may not ring. OBi 20x devices do support simultaneous ringing, but not 1x0 devices.
You can avoid this issue by creating a new, dedicated Google account to host the GV phone number. You can then use the number transfer procedure to move your existing GV number over to the new account:
https://support.google.com/voice/answer/3527591?hl=en&ref_topic=1708124After changing GV accounts, go through the OBiTALK web portal page procedure to change your OBi's GV configuration, to use the new account.