please use default .htaccess from CI4.
replace this line:
RewriteRule ^([\s\S]*)$ index.php/$1 [L,NC,QSA]
with this line:
RewriteRule ^(.*)$ index.php?/$1 [L,QSA]
Then,set:
App -> Config -> App.php :
public $indexPage = ''; //'index.php';
This is working for me.