First, it isn't clear if the 12.5 release was officially released or not. It seems so as it's available to download on the 3CX download page. Well, we got the issue of being using a 32bits system that seems not to be supported anymore. We installed a new 64 bits OS to replace our IP PBX and proceeded with the common restore of a previous backup of v12 (SP6). The PBX started up but we had two issues: 1. The phones weren't registering to the PBX. While analyzing the issue we found that the interface where the phones were provisioned with was changed to the public one that has no connection to the phones. Before, it was set with the private address like shown bellow. This happened to all our extensions and we needed to change one by one. 2. When someone called to our PBX the greeting starts but doesn't allow you to dial any extension or select the options presented. You also aren't able to hear the one calling while they are able to hear you. So, we thought something went wrong with the migration to 64 bits. New VM, new configuration, something we did wrong for sure. So we did a new try and started from scratch again. This time we installed v12 SP6 (the one we had before) and did the restore of the backup from the other PBX. This worked as expected. No issue with phone registration and no issue with incoming calls. So, next step was to upgrade this working installation. Well, the outcome was the same as the first try. Extensions not being registered because of wrong configuration and hearing incoming calls plus dial tones not working again. We had to revert but we wonder what changed in 12.5 that doesn't work well with our setup. We found a bug or 3CX won't work anymore in the special design we use? Attached is a diagram of our setup so it's understandable how we work. This worked well since v8 when we started to use it. Any insight or help will be appreciated.