I was able to get my obi202 on firmware 3.2.2 (Build: 5898EX) to update the timestamp about every hour when I check the "MWI Subscription on" timestamp on the anveo SIP Device Registration page.
I did this by going into Expert mode configuration and checking "Device default" for the X_MWISubscribeURI setting for the anveo SP. This cleared the url that basic mode had set and upon a restart of the obi202 has been checking in all day, about once an hour as per the timeout default of 3600 seconds. I have yet to test leaving a message and reading it to fully validate the functionality but I would hope this fixes the issue.