Any biometric method may present some rejection problem, because they involve human and biological characteristics. That means that even a person whose fingerprint is already recorded may not be recognized. This is called "false rejection" and happens with any technology and manufacturer.
This problem rarely occurs (below 0.1% of the cases), but it is important to keep this possibility in mind during the implementation, so you can plan on what to do if that happens. The individuals that present this kind of situation are the elderly and children up to 6 years old. Some chemical products may also provoke the temporary reduction of a fingerprint quality. In addition, some people don't have fingerprints on some periods of the year, due to biological conditions associated to weather or to their own organism. In these cases alternative methods must be used, such as use of documents, passwords or access cards.
However, many false rejections happen because of an error during the registration, with the capture of a partial fingerprint, usually the tip or the side of it. That increases the possibility of a rejection, because the next time that fingerprint will be read, the captured image may be a different one, not registered yet. A correct registration is the best way of avoiding a false rejection.