I can't get my dreambox 500C working

Hi,

Can anyone help me, I'm new to all this and don't have any technical knowledge. I bought a dreambox 500C recently and it is supposed to be plug and play but I can't get it going. It comes up "All known transponders have been tried but no lock was found. Check antenna/cable set up or try another satelite/network. I am with N*L MMDS digital. I'm in county Waterford, Ireland. I've tried changing the codes but I'm not sure if I have the right ones.Id really appreciate any help at all. Thanks a mil.