With two of the same model OBi devices, at home, plug in only the working one, and confirm that it indeed works with Google Voice, and note the GV account to which it is authenticated. Unplug it. Plug in the other OBi. Go through the setup procedure and configure it to the same account. If it doesn't work, then you've done something different with the configuration of the two boxes; GV couldn't care less which OBi is connecting. In particular, compare the firmware level of the two OBi units, and make sure they're they're at the latest available level, 2872. If not, update them accordingly.