Hi, First, clean the disk drives read/write heads with a cleaning disk, do it 4 or 5 times. After letting solution evaporate for a few minutes, take a new disk and try to format it, if it works, then copy files to the disk, try reading them, deleting, renaming, etc...
As for jumpers, first, this is an
External drive, right, like an A1010? If so, I can't see how jumpers (actually jumpe
r), could have been changed. There should be only one jumper on the back of some Internal Amiga floppy drives, to select between DF0: and DF1: Assuming I remember correctly.
I suppose if nothing works, you could take the drive out of the external enclosure and check the jumper, but I have no idea why someone would have changed it.....
And then again, your drive might be dead....I have had 2 A1010's, only one works....
Hope this helps...
Edit: Just remembered: my dead 1010 drive gave me that DF1:

? bit, too....Hope it's just a cooincidence....