I don't know if this will help, but I was assembling an A3000 last night. I mistakenly plugged the ribbon cable in upside down. When you do that the floppy drive light is on all the time (and of course the drive doesn't work). It did not damage the drive.
Check that all the little sensor pins near the front of the drive are depressed properly when a disk is in....and that they also pop up correctly when the disk is ejected. One might just be stuck down. They are black and are near the front of the drive (you can only see them when the Amiga's cover/faceplate is off.
