I'm having the exact same issue.
I just purchased an OBi200 to replace my aged OBi100, and after adding the device and it showing online under the dashboard, it keeps saying "Firmware upgrade needed. Cannot upgrade [number] since it is offline. Please try again when it is online" when I click the "Google Voice Set-up" button.
The device is obviously online because I can go into expert mode and it has no trouble pulling the settings from the device. It is running firmware 3.2.2 (Build: 5921EX). I tried downgrading to 5859EX, and after about 7-10 minutes when it was accessible again, it was still on 5921EX. Maybe it downgraded then auto updated? If I try uploading the 5921EX firmware, it says it's the same version and refuses to upgrade.
I've also tried the steps in the linked article (although being a brand new device, it shouldn't require it), but no luck.