Welcome, Jamietmob!
There are many good suggestions and instructions in this thread:
https://www.mobileread.com/forums/sho...d.php?t=142035. Hopefully, something in there will work for you if krewskater's very good observation hasn't already cured your PEs ills!
P.S. According the pyxiwulf FAT does work, and might even be better than FAT32.