I guess you have tried the obvious, removing the power cable, wait 20 seconds or so, and then re-inserting it, waiting a few minutes, then turning the box on?
Alternatively, you could force a new software download by again removing the power plug, pressing and holding the "backup" button on the top of the unit. While still holding the button down, carefully re-connect the power cable. After 10-15 seconds a black and white picture should appear informing you of a software download in progress. At this point you can release the backup button. Leasve the unit to finish the download, usually 10-15 mins, then try to turn on. If this doesn't work, seeing the installation is so new, call Sky to arrange a replacement. Most modern electronic equipment, if defect, will fail during the first few weeks of operation.
Hope this helps!