Manicures usually look shiny right after you apply it.  But after a while, it starts looking dull.  Like the other day, my new gel polish, which is supposed to be real shiny, was looking dull... like this...

Before: dull nail =(

There are different causes to it, you might have smudge the topcoat a bit, it might be the quality of the topcoat, but more than often, there's oil on your finger nail.  It can be from your hand cream (I experience this a lot), touching your face (the sebum on your face), or any other source of oil.