A suffragio di tutto ciò, cito la guida del .com:
Detto questo, sembrerebbe che manchi la funzione della virtual root dichiarata in qualche file.Let's start with the the simplest case :
phpBB vanilla (no modification what so ever) to phpBB SEO premod same version
Here we'll assume that we are talking about the latest version (for both phpBB and the premod) since there would be no point to do it on an outdated version (we'll talk about updating phpBB and go to the premod later).
In this case, it's very easy, all you would have to do would eb the following :
Upload all files from the root/ directory of the premod package to where your phpBB is installed, EXCEPT config.php and install/*.*
At this point, your forum should work exactly the same as before.
Go to example.com/phpBB/phpbb_seo/phpbb_seo_install.php while logged in as admin and founder, and just go through the install procedure. This will activate the phpBB SEO ACP module which will handle the settings.
If you also want to use GYM sitemaps & RSS, go to example.com/phpBB/gym_sitemaps/gym_install.php while logged in as admin and founder, and just go through the install procedure. This will add the GYM sitemap ACP module in the phpBB SEO ACP category and will install the mod's db table.
Now you can proceed with setting up all the options of the mods in acp, and generate your personalized .htaccess.
Poi... posso sempre sbagliarmi.