If the original is not placed correctly, it cannot be detected.
See the link below for instructions on how to load originals into the scanner.
Combinations of Originals and Scanner Position
Placing Standard Size Originals
Placing Large Size Originals
Placing Long Paper
Placing Plastic Cards
Placing Laminated Cards
Placing a Passport
Placing Important Originals or Photos
Placing an Envelope
Placing Irregular Shaped Originals
Loading Batches of Originals with Different Paper Types and Sizes