Will Sigil Open the file (bypass Open With PI)
Ctrl-o with the book selected:

O, just plain ole 'O'
then right-click the file: Open With... (this is the OS file managers O/W

)
The book my be defective
FWIW, I use this PI frequently with Sigil.. It just runs.
The only change I made, was when I migrated my config files from 32bit (XP) to 64bit (W7-W10)