The most common questions, and where to look first.

Large files failing or timing out

Raise the Default max. upload size if that's the actual cap you're hitting. With remote (FTP/FTPS/SFTP) storage, the whole file travels over the network during the final "assemble and store" step, which can hit max_execution_time or a timeout on a reverse proxy/CDN in front of the site - test with a genuinely large file before relying on remote storage for big transfers.

A file type gets rejected

Check Allowed file extensions first; if it's filled in, that's the only thing being enforced. Otherwise check Blocked file extensions.

Expired transfers pile up instead of disappearing

Confirm a Scheduled Task using the Delete expired Filedrop transfers routine exists, is enabled, and that Joomla's scheduler is actually running on your hosting (cron or web-cron).

The upload page redirects to a generic URL

Create a Filedrop - Upload menu item; without one, Filedrop can't build a proper SEF URL.

Guest access password doesn't seem to apply

It only gates visitors who are not logged in. Test in a private window, or log out first.

A download link still works after it expired, or without the password

Check whether your storage folder sits inside the website root and your server runs nginx. Filedrop protects that folder with a .htaccess and a web.config, which nginx ignores, leaving the stored files reachable at their own URL and bypassing every check Filedrop performs. See Keeping stored files out of reach on the Configuration page.

An older transfer's file can't be found after renaming a Joomla user

This only affects storage folders that use the {username} placeholder, and only transfers created before Filedrop started recording the uploader's username on the transfer itself. Renaming the account moved the folder those older files were looked up in. Either rename the account back, or move the affected files into the folder the new username resolves to.