I am having issue with OS 7100 at 2 different sites with same issue. Both have SIP trunks that are working fine until one of these 2 things happen:
1 - the system experiences a power-down/power-up
2 - or if the internet goes down and then recovers

The OS7100 will not reconnect automatically to the SIP carrier when the phone system powers up. I have to go to 5.2.13 "sip carrier options" to disable the SIP server and then re-enable, save, and refresh about 4-6 times to get the connection back on line. I have upgraded the software to 4.95 but was not a solution. this is causing me alot of pain and embarrassment. Any suggestions would be appreciated!

What version of software are you running?

There was a problem i found in 4.8x and/or 4.9x where if you have an entry in the registra address it wouldn't register after a power failure. Requiring you to disable and re-enable the sip server to get it working.

I can't remember if they fixed it in 4.95 or not.
I'm going to go over the notes and post more when i find it

Ok in 4.95 they fixed my issue as follows:

When Registrar Address was set, the Proxy Domain Name was not used as the host of REGISTER.

I had this a lot in 4.82, it didn't exist in 4.75

4.99 is out in the US I believe, though there is nothing mentioned in the release notes about it.

Also check the alarm logs as from 4.75 and up you get sip error codes which tell you why the registration is failing.

Thanks for the inputs here, I will look at and try these suggestions. I just downloaded the 4.99 version and will also install while I am at it, starting with our in-house system. I will circle back with input with any success/failures.

I have found that if you set multiple DNS servers to on that it fixes the problem. This was also a issue I was having a lot and that fixed my issue.