Recently we installed ESET Endpoint Security for a client in two different locations, both locations using older model Telstra business Modems. The installation was problematic from the start with registration errors and the modules would not update in both locations. By chance the client had FTTP installed while all this was happening, which included the installation of the latest model Telstra Business modem. Once the FTTP was installed and the new modem connected, all the problems were remedied. I believe this problem is not unique and a replacement modem would be a good place to start.