Not sure what the contents of the text you received says, I would think it's related to the new install.
The Optus @ Home app does have a Support section that includes a modem installation step by step guide.
I installed and ran it before the switch to NBN. This gave me my current speed (5Mbs) and connected devices. I could also see the NBN install instructions.
I ran it again after connecting my tablet and devices to the NBN to see they were all there and confim the speed was around 40Mbs.
Nice one! It is a really great app. ☺️
Thanks for coming back to Yes Crowd to let us know.