What if my radio code don't work? And its from the dealer

the radio code is in the glove box stamped on a label on the side..forgot what year Honda/Acura started this,because they use to put it on an index card inside the owners manual people would see that card and manual and just put them somewhere and then forget where they put them.if the dealer gave you the right code and you are entering the correct code,then the radio should come on,unless one of the previous owners replaced the factory radio with another Honda/Acura radio at some point. what did the dealer ask for when they gave you the code,the vin or the serial # on the side of the radio?