2022 Experience with "Registration Not Required" during setup for Google Voice: I also received a Registration Not Required message during setup in the configuration screens after a few minutes of the device attempting to configure. When I attempted to place a call after that, I was receiving the "[phone number dialed] did not receive a response from the service provider" error. After a couple of attempts to repeat registration, I found this forum online and the instructions to update the firmware if I saw the triangle warning sign icon on the setup screen (which I did).
Updating the firmware did work, however I needed to download the firmware file linked from
http://www.obitalk.com/forum/index.php?topic=9.0 and upload it directly to the OBiTalk device connected to my LAN. In order to access the device portal, I dialed "***" from a phone connected to the OBiTalk device, then selected option 1 to have the device local IP address read out. To log into the device from a web browser (on a device connected to your LAN) and make changes it asked for an admin password. The device I purchased secondhand still had the default password set so I could complete the process of uploading the firmware file I saved locally. I knew the firmware update was in progress because the status light on the OBi202 device was displaying red during the update.
The phone and fax devices I have attached to the device are now able to successfully complete calls.