Shoo, you need to reconnect your printer to the WiFi (if it's a wifi printer) and then delete and re-add the printer to your computer.
This has nothing to do with NBN as such, is more about the change in router.
I'm a Yes-Crowd Contributor, not an Optus Employee, and I contribute on a voluntary basis. Did someone on Yes Crowd answer your question? Did they share a great tip Please remember to acknowledge their awesomeness by throwing a Kudo and or Accepted Solution their way.