Any ProDOS or MS DOS volume originally formatted as a Macintosh volume may not work with PC Exchange. It seems certain Macintosh residue (boot block information) is left on the drive so PC Exchange is confused at the Macintosh-like characteristics. Since PC Exchange sees the drive as a Macintosh drive, it just ignores it and won't mount as a MS DOS or ProDOS volume.
The solution is to perform a low level format on any Macintosh volume before formatting it with a non-Macintosh operating system. This low level format (with some Apple II or DOS utility) eliminates Macintosh boot block information from the drive so PC Exchange won't see it as a Macintosh drive.