The most important part of a successful installation is preparation. Dust and moisture are the two main culprits for preventing adhesion.
Think of our wallpaper like a giant sticker. The walls will need to be free of dust, cobwebs or any other residue that may accumulate on walls or else the wallpaper will stick to that and not actually your wall!
Also make sure your painted walls have cured, which can take up to 4 weeks!