I had an older version running on a standalone XP machine but started having some issues. I did a clean install in a VM (under XenServer) of a clean install of XP Pro with all the latest patches. So 3cx is v9 SP4 with all updates. I created everything from scratch again. There are four SPA3102s labelled PSTN-1 to PSTN-4. PSTN-1 is connected to a Verizon POTS line (the "office" number), PSTN-4 is also connected to a Verizon POTS line (the "home" number), and PSTN-2 and PSTN-3 are connected to the "POTS" outputs of a Vonage adapter. Lame going VoIP across the Internet (Vonage) to an adapter to go to POTS and then through a 3102 to get back to VoIP, but ya do what ya gotta do since Vonage doesn't support SIP trunk. PSTN-4 goes to a ring group 24x7. PSTN-1, PSTN-2, and PSTN-3 go to different Digital Receptionists depending on the hours. PSTN-2, PSTN-3, and PSTN-4 all work fine. When I call the "office" POTS line plugged into PSTN-1, it just rings and rings forever and nothing happens. If I plug that line into one of the other 3102s, same thing - continual ringing but no answer. If I plug one of the Vonage "POTS" lines into PSTN-1 and call that number, it works fine, too - so it isn't a failure of the PSTN-1 3102 configuration or 3cx's config of that line. Ok, so it sounds like the line isn't working. Except that I can call OUT from 3cx using that line and have no problems (I setup "81" to "84" prefix rules to allow selecting a particular outgoing gateway). And if I plug a test set into the line (instead of the 3102), it rings just fine, I can call just fine, I can answer a ringing call just fine, etc. If I tell Verizon that there's a problem, they're probably going to tell me I'm nuts. The 3102s were all updated to the latest (5.1.10(GW)) firmware, all are the same hardware level, and they were then configured exactly as per the instructions found on the main 3cx web site (from the "how to configure gateways" documents). I tested and noticed that the polarity was backwards on this one line. Actually, this one was CORRECT and the rest were all BACKWARDS, but I reversed it to match the others. Same problem. I'm wondering if there's just something weird about the configuration that's causing problems with a perhaps slightly out of tolerance line, or perhaps CID is being reported slightly differently on this line. Whatever, it is driving me crazy. Anyone got any ideas?