I also have the same problem. I have a Google Home too and the problem seems to have happened after telling Google Home to use my Google number to make calls. The phone attached to the Obi rings, I answer but nobody is there.. the phone stops ringing. I get a notification there is a voicemail and that's where the call went to. It's like I never answered the phone. If I use Hangouts to make the call on my wifi from another cell phone, everything is fine. It seems like the problem is only from outside calls.