Lets go through some reset options that have worked in the past.
Put the T-Box into "sleep" mode:-Press and hold the power button till you see the banner "entering sleep mode".
Remove the power cable from the T-Box, wait a few seconds and plug it back in.
Meanwhile (just for good measure) turn your router off and back on again to reset it.
Turn the T-Box back on and see if it corrects the problem.
Go to the menu on T-Box then go to
Other Reset Options
There is a reset button on the bottom of the T-Box.
Press and Hold Reset
Release once the light on the front has flashed ONCE
See how this goes before we try a full reset.
Have you recently got Foxtel by any chance?