Yes, old OBis work with GV but they need a firmware update. It is no longer possible to configure GV using the ATA's local web server GUI. You must use the Obitalk portal. When you do you will be told that a firmware update is needed. You will probably also be told that as the device is out of 1 year warranty you need to pay $10 for 12 months support to enable automatic upgrades.
However you can still update manually at no cost. There has been discussion of this on the forum in the last month or two.
Also search for instructions by SteveInWA for configuring GV on OBis amd follow them to the letter.