It should turn on when you push the butoon in, old it for a second and it will beep (turn blue) release then your ready to go (press and hold again for eyes off)
Sounds like the button has slipped slightly out of place mate (guessing the royal mail werent very gentle when moving it) If you cant get it to sort by taking the frame off and putting back together then ill give Lump a shout (it will take him a second to do and ill get him to show you what to do if it does it again)