There could be several reasons why your scanner is not detecting your document.
First, the document may not be placed correctly on the scanner. You should ensure that the document is facing the correct way and laid flat on the scanner for it to be detected.
Second, the settings on the scanner could be incorrect. Check that the correct resolution and file format are chosen, as well as any other scanning options like deskewing or color modes.
Third, the document itself may be difficult to scan. If the document is old or damaged, it may be more difficult for the scanner to read it. Additionally, make sure the document is free of debris such as smudges and dust particles.
Finally, the scanner could be broken. If the above solutions do not work, the scanner itself may have a malfunction and needs to be serviced.