If you are getting an error when using Gravity Forms or the Dropbox add-on that says FAILED (Temporary file could not be moved), FAILED (upload folder could not be created), or Upload folder is not writable, there are a few different problems that could be the cause. Here are some troubleshooting steps that should help you track down the issue and solve the problem.
The information below is also applicable to log files not being created when logging is enabled.
Check Folder Permissions
Most often the error is caused by incorrect folder permissions within the wp-content/uploads directory. This is a standard WordPress upload path that will need to be writable before anything can be saved to it. Note that permissions can be different per folder, so you can have write permissions for the folder wp-content/uploads but not for wp-content/uploads/gravity_forms or a subdirectory of this.
To correct this, take a look at your file permissions on the server. Often times it’s as simple as setting the permissions correctly to 755 or 775, but this may vary based on your hosting environment. If you’re not sure how to change your file permissions or what your permissions should be, your web host will be able to point you in the right direction.
Check Folder Ownership
Another common cause for this error is the folder ownership. If the folder is not owned by the same user running the web server service, WordPress may be not able to perform write operations in the uploads folder. Changing the ownership of a folder can be done only by a server admin, so you will want to contact the web host and ask them to ensure WordPress is able to write under the path wp-content/uploads/gravity_forms and any folder below that path.
Check PHP Settings
While somewhat uncommon with modern web hosts, you might have Safe Mode enabled on your PHP configuration. To properly save content from WordPress and Gravity Forms, you’ll need to disable Safe Mode.
If you don’t know how to do this on your own, your best option is contacting your web host.
Ensure File Isn’t Potentially Dangerous
Many web hosts will block the upload of files that could be potentially dangerous such as .php files.
To allow these types of files, try including them within a zip file or contact your hosting provider for other possible solutions.
Typically, a great deal of information can be exposed when using the Logging.
When looking through the logs, locate lines that contain GF_Field_FileUpload.