In Writer, scanner screen is blank when you select source. Works fine in other apps such as OpenOffice and Word.
You may be interested in reading tdf#114635 put in See Also.
Also what's the brand and model of your scanner? What's your Windows version? Did you install TWAIN drivers for your scanner?
HP LaserJet Pro MFPM125nw WIN10 Twain32 driver No TWAIN64 driver available from HP
This is fixed for bug 114635. Where use of the 32-bit TWAIN drivers is provided for the upcomming 6.3.0 Alpha release and on current master dev builds. The feature will not be backported to the 6.2 branch releases that require a 64-bit TWAIN driver. And, as noted in bug 105762 there is also no support for WIA driver which other applications may be using. A dup of bug 114635, but marking here as WF for 6.2 branch.