Dvd Burner Will Not Recognise That There Is A Disk Inserted.

[JIMCON]

I Have An External USB 2Liteon Sohw 812sx Dvd Burner, But It Has Stopped Recognising That A Disc Is Inserted, Although The Operating System (sp) Tells Me The Equipment Is Operating Correctly, The Fact That A Disk Is Inserted Is Not Recognised.
I Have Flashed The Latest Firmware, No Change.
It Was Working!!
Can Anyone Help To Solve This Problem.