Why isn’t paper being detected/ recognized when inserted into the scan

My Neat scanner NC-1000 has operated without incident for many years. Just the other day it stopped sensing/detecting paper/documents inserted waiting to be scanned. Even the little orange triangle below the SCAN icon does not appear. I have cleaned and followed every procedure I could find but none deals with "failure to sense/detect paper. Is there a sensor that is not visible that the paper triggers that stopped working? Could something have become "loose", not making a connection? As far as I can tell it is NOT the "little black finger between two plastic flaps. It pops in and out like it is supposed to and does not appear to be stuck. Thank you