Start with administrator cache cleared and a hard refresh. Most File Desk issues are permissions, path config, or MIME rules.
Upgrade to 1.0.5 or newer. Early 1.0.x builds mis-ordered Web Asset Manager arguments and could white-screen before the template rendered. If blank persists, enable temporary PHP error logging on a staging copy and check for fatal errors in HtmlView or missing jQuery.
Upgrade to 1.1.15 or newer. File Desk loads image previews through the CSRF-protected connector when public {volume}/.tmb/ URLs are blocked on the host (common on Joomla 6). Requires PHP GD or Imagick and a writable storage path. Open a folder of images and wait a moment for thumbs to generate.
Upgrade to 1.1.13 or newer. Early packages omitted the component media CSS folder, so filedesk-cwd-thumbnails.css never reached /media/com_rca_filedesk/. Switch to Thumbnail View first; the Preferences slider applies only in that mode.
Upgrade to 1.1.12 or newer. Use View → Thumbnail View explicitly. List ↔ icons toggling is separate from Thumbnail View.
elFinder stores generated thumbs under the configured volume. Requires PHP GD or Imagick and writable storage. Use 1.1.4 or newer if dotfile access blocked .tmb writes.
Confirm Path resolves to a folder under the site root (relative paths like images are fine). Check that tmp/trash exists or can be created. Verify the user has core.manage. Open browser developer tools Network tab and inspect connector responses for Invalid Token; that means CSRF mismatch—reload File Desk to refresh the session token.
Upgrade to 1.1.2 or newer. Some hosts symlink common folders (for example images) to shared media outside the virtual host tree. Older builds treated the symlink target as the jail boundary and rejected a valid Options path. Current releases validate the configured path under JPATH_ROOT and still use the real folder on disk for elFinder.
With Restrict Uploads on, add the MIME type reported in the error to Legal MIME Types. With restriction off, look at filesystem permissions or host upload limits instead.
Review Advanced Permissions lines for typos, wrong group IDs, or missing paths. Remember group 1 bypasses the map. Users in multiple groups receive the first matching line in map order, not a merge.
Installed version may be equal to or newer than the feed entry, or the site still points at the old public feed from 1.0.3–1.0.5 free builds. Install 1.1.0 Pro or newer so manifest updateservers aim at the private feed, then confirm production feed and L2 ZIP match on recreatinganew.com.