I see you also asked here:
http://www.dslreports.com/forum/r31099350-Voip-ms-Trouble-With-Obi-200-call-rejected-by-service-providerThis looks like a Rip Van Winkle bug (you just woke up from a long sleep and didn't know what went on while you were out of it).
Error 500 means that the server to which the request was sent can't respond and gave up.
Error 503 usually means that the service is unavailable...because the service is down, or either the service itself, or your right to use it, is shut off.
Since you said you've been using it for "years", you probably need to take care of something over at the Simonics (not Simmons) gateway site to reauthorize your account. Because GVGW is, in fact, a XMPP/SIP gateway, there are two separate points of failure: The gateway could no longer be authorized to use the Google Chat/XMPP service on
your Google account, or your OBi has some sort of login problem to the SIP side of the gateway. You'd know the latter was the problem if the status on your OBi doesn't say "Registered".
Since Circlenet is out of business, that response would be expected.
Why not just use Google Voice directly with your OBi?