A few factors can cause issues with Gravity Forms produced links generated to permit downloading of a submitted file. This includes links to files in a post, entry, or form submission email notification. This issue only applies to links which contain the gf-download or gf-signature query string parameter. Direct URLs which are stored in the entry within the database are not affected.
Some common causes (ordered from most common to less common):
- A theme or plugin conflict, such as blank lines after closing PHP tags in .php files. Try running through a full theme/plugin conflict test.
- An outdated PHP version. Refer to the Gravity Forms System Requirements article for details.
- A redirection plugin or .htaccess rule conflicting with the download URL.
- A caching or security module configured on the server.
- Redirecting uploads to a custom location using a filter or plugin.
- An email service such as SendGrid replacing the functional file URL from the notification with an invalid tracking URL. Deactivating the email services click/open tracking for links has resolved this issue in the past.
- The salts in the sites wp-config.php file being changed, invalidating the hashes which are included in the links. This can happen if you’ve migrated your site to a different server recently or if you’re using a security plugin (e.g. Sucuri) to automatically change them. If that is the case, you can get the new download links from the entry detail page.
Once the above causes have been ruled out and the issue remains, the next step would be to contact your web host so they can check for server side issues.