You write "the" floppy. Just a thought... if the floppy is as antiquated as the computer and OS, maybe it is corrupted or (partially or completely) erased?
Floppy disks are vulnerable to damage by factors including magnetic fields, moisture, humidity, heat, mould ("mold" in N. America), and just plain age.
Suggest you try creating a fresh boot floppy using a recently purchased blank floppy.
Possibly CMOS battery is flaking out? Are the system date + time as shown in the BIOS setup correct?