index.php

installed and mostly working.

however the link to topic inside a forum gets ‘link not found’
https://richardborg.org/command-and-colors-napoleonics/test-topic

if i manually add the index.php to this URL which is used by all my other pages it now works
https://richardborg.org/index.php/command-and-colors-napoleonics/test-topic/

my permalink is
/index.php/%postname%/
which if changed to remove index.php breaks all my static pages.

The page I need help with: [log in to see the link]