OK< am back. AM in middle of moving office at the same time. WIth regard to what SY indicated, I agree with him and this is what I have been indicating since I first suggested a wireshark capture a couple of weeks ago. However, sometimes providers can be hard to convince so a capture will help.
BTW, please do not buy a lotto ticket. Given your track record with getting a stable system up and running, it would be a waste of time.
Wireshark -
1. If possible, limit the amount of traffic on the network. It really doesn't hurt anything, just makes it all a little faster and easier to deal with.
2. Get your fax arrangement set to send a cover page or something very simple, 1 page.
3. Ensure that the fax server is running and that the extension is registered and showing green.
4. Start wireshark and let it start to display the data on the screen.
5. Send the fax and if possible watch the system extension status page for the fax extension 888. You want to see the color for the extension so as to easily confirm that the system does indeed see the incoming call, it gets answered and then hangs up.
6. Once you have the hang up, you can then stop the capture, but do not close the program or discard the data.
7. Do not post the data to the forum as it contains info that is best kept to yourself; or post, but edit so as to hide some of the ip addressing, say the last 4 to 6 digits.
8. You should also click on file and save as and then give the file a name you can recall. This file may be what is sent to your provider so that they can see the issue should that prove to be necessary. Also, as an aside, many/most providers can monitor a call in progress and can see the issues in real-time.
9. With the wireshark still up and the data present, click on the telephony tab and then from the drop down, the Voip calls. Wieshark will return with a box showing what it determined to be Voip call by displaying the telephone numbers.
10. Select the calls of interest and highlight, and then select display flow. This will then return a graphical, chronological sequence of events associated to the call along with the IP addresses associated thereto. This is apt to be the most telling as you will be able to see the various invites from start to finish, who offered what and the response to same. If need be, you can then also highlight and click on one of the events and wireshark will take you back to the data of interest so that you can examine the packets in detail.
If you will send the pcap file to me, I will do the above as well, but will try and highlight the issue so as to make you aware of what to look for in the future. I will send you my email in a PM.