It looks like your .htaccess RewriteRule is what is blocking it. I highly recommend disabling or revisiting that rule as it will cause issues with the wiki itself as well -- you will be unable to view or edit any page with a . in it followed by letters. What is that rule supposed to be protecting against?
To be clear: it isn't failing to find the files. You are getting 403 Forbidden back. Your RewriteCond is checking for a query string containing a period followed by anything EXCEPT a bunch of special characters. So having something like ".styles" or ".css" in the query string will trip it. You can verify this yourself by attempting to view the page http://wiki.tri-sen.local/index.php?title=MediaWiki:Common.css -- your browser will display a 403 Forbidden page there as well.