Solved: Connection Problem with Telstra Smart Modem

I'm posting this in case it helps save someone the hours I spent trying to get my Ring Doorbell 2 to connect to the internet via a Telstra Smart Modem Gen2. A feature of this modem is that it contains a SIM card and will connect to the mbl network, if the hard-wired NBN network goes down. It is often the case that the modem arrives for a new installation before the NBN line is physically connected, in which case the modem operates using the mbl network from the get-go, until the NBN cabling is completed. Out of the box, the modem in mbl mode connects to a Ring security floodlamp (and perhaps other devices...I don't know) without any problems BUT it won't allow the Ring 2 doorbell to connect to the i/net: you will hang up with two lights on the left of the ring flashing and an error message. The solution is to go into the management portal of the Telstra Gen2 Smart Modem and go Advanced/Internet/LTE. Scroll down to Mobile Configuration and find a window labelled "PDP Type". The default you are likely to see is "IPV6"...which is blocking the Ring2. Instead, select ("IPv4v6"). Save, then re-start your install process and it should go smoothly.