Welcome to the Community!
I'm sorry to hear about the disruption of your service. It seems that you've already spoken to our Technical Team earlier and at that time your connection was already up and running. However, your connection is down at the moment. Our tests show that your NBN box is offline. Can I confirm if you are purposely turning the devices off (NBN box and modem) when you're not using the internet?
Is the slow speed issue occurring on a specific time? Have you tested the speed via a WiFi or a Wired connection?
We've created an article which will guide you on how to troubleshoot a slow speed issue. You may refer to this link.
If you are using a WiFi connection, you may also check this link which will guide you on how to improve your home network.