If you pressed the reset button, you should login (admin/admin) to the modem configuration to check the settings, mainly username and password and maybe some others that were provided in TPG's notification.
You can try power cycling your modem to see if it completes the auto config process.
If it doesnt come back on with the ''internet light'', you can try a manual configuration.
Please find an attached link for a guide to help you configure your modem.
If yours is not VR1600, procedure will be similar.
So, the internet light is on for a moment and goes off?
Is the DSL light (next to internet) on or off? It needs to be on first.
What are the lights on the nbn connection box if you have one?