Perhaps your floppy drive is dirty the reader head or that the this floppy drive is bad, for example the grease the mechanism is dry, you can try use one floppy from PC of 720Kbs that runs fine and instead the original Amiga, only that the autorun the disks not work with this floppy unit, but is a fast test of your system, because open the the unit, humm, I have bad experiences, because after the unit doesn't work for me.
