Please try unplugging it for approx. 30 secs and connecting it again. You may need to try this a few times.
Is it connected via WiFi? Any different with a direct connection (or vice versa).
If it stays on long enough, you may need to do a soft reset or a hard reset.
If none of that works, you will need to contact Optus directly for further troubleshooting and if needed to arrange a replacement.