After several days of my OBI200 not working, trying dozens of things - I discovered the problem and wanted to share because I thought it might help others.
I have a zytel router with Century link DSL, and all worked fine. When I went into router admin and set a time-of-day restriction on a completely different IP address, then both of my VOIP services in the OBI could no longer connect. Removing the restriction solved the problem. Note that the time of day restriction was not in effect at the time, even for the IP address it was targeted for, much less the OBI.
Somehow it seems setting up the time-of-day restriction kicked the router into some other mode where it was messing with all the traffic. Removing that restriction solved the problem.
Any idea why this would be, is there some way to avoid this?