The Amiga (all models) made heavy use of the disk insertion switch, which is located on the left side of the disk window (near the write protection switch).
That switch commonly simply get stuck on or off, stopping the drive to detect if a disk is inside, or even detecting a "ghost" disk that isn't there.
Simple solution: get a drop of isopropanol (also known as IPA, alcohol spirit and other names) on the switches (an hypodermic syringe will help) and actuate them a dozen of times, then let the alcohol dry for a few hours and test again. Chances are that this simple thing may cure the drive.
