Since this has been a recognized issue by Samsung and other users, I will use this thread to give you the repair options and also to urge Samsung to GET IT FIXED. Some users may try using the scanner only for it to not detect any input at all. This issue seems to have only started happening after a recent update, it also appears to be a software issue, not the scanner itself. TO FIX THIS TEMPORARILY you have two options: you may restart the phone or back up your files and do a hard reset as advised by official Samsung support. I would also like to urge Samsung to have some people comb through the last update file to check for anything out of place and release a patch for this and any other issues the Galaxy S8 has.