I just now tested it with an OBi 200. The device was configured to use my GV account "A". First, I made sure I was logged into the correct / different GV account "B", not "A". Then, using the OBiTALK portal, I clicked the SP1 link, and then I clicked the "Click here to replace the active Google account" link. The portal made the change immediately to "B" after I confirmed the account I wanted to use. The OBi then rebooted, and came back up using my GV "B" account.
Carefully follow the instructions and visually confirm that the Google account name displayed on the screen matches the account you want to use. It is very easy to be logged into the wrong Google account, since Google allows you to be logged into multiple accounts on the same browser session. Watch the blinking LEDs on the OBi after issuing the command. If they don't blink, indicating a reboot, then pull out the power plug and re-insert to force a reboot.
If you aren't immediately seeing the account change, then you're doing something wrong, or the portal is temporarily down.