How to access subdirectories?

Quite some time ago, I remember not being able to access WP installs in a subdirectory. I don’t remember how I made changes in order for this to work. Can someone help me?

Example: I have a WP install at https://www.mydomain.com and a WP install at https://www.mydomain.com/WP2install

I am getting a 404 error at: https://www.mydomain.com/WP2install, rather than the WP showing up.

What do I need to change or add to the .htaccess file?

Here is what is currently in my .htaccess file for the main site, not the WP2install.

# To set your custom php.ini, add the following line to this file:
# suphp_configpath /home/yourusername/path/to/php.ini

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

# END WordPress

I know there are lots of topics on this, but none of them make any sense. I can’t seem to figure out what I need to add to this.