Home page not found but working fine (pos. permalink prob.)

Hello, i’m having a really strange problem with a WP install.
WP is installed in a /subdirectory but the domain is redirected to it.
Site url changed to domain, WP url remains unchanged, permalinks generated. I’ve done this many times with no problems at all.
Permalinks work fine for pages and posts https://www.domain.com/page_name ect.

The problem is only with the homepage:

• When entering main domain it displays url: https://www.domain.com/installsubdirectory
• In the browser title I get ‘Page not found’.
• But the Home (as a 404 redirect) is loaded and working fine.

Standard htaccess:

RewriteEngine On
RewriteBase /installdir/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . index.php [L]
</IfModule>