[dar512]

Are you trying to read or write?

My experience with 3.5 floppies is not good. I've had them go bad in two years or less. Some I couldn't even reformat.

First try blowing some canned air into the drive. The 3.5 drives are more susceptible to dust than the old 5.25 drives were.

Try formatting, filling then reading a new disk. If that works, I suspect your old disk has gone bad.