Usually the first reason that decals or labels fail is that surface was not cleaned properly. I have had people tell me that after they have tried to place decal on a surface and won't stick then they clean surface.

The surface needs to be clean and free of any oil or grease and at room temp. Not igloo room temp either. Most suppliers have a min temp of 45 degrees at which vinyl will stick to most or all surfaces.
Thanks and hope this helps some with similar problems or maybe can avoid any problems.