The auto upgrade method fetches the latest version from our server and attempts to extract the contents over the existing files. Whether this works or not depends on whether your web server has permission to write to the file structure. In many cases it won't.
- use the manual upgrade method.
- set all files and folders to be temporarily writable and try again.
If you choose option two you can either use your favorite FTP client to set all files and folders to have a chmod value of "0777" recurring or if you have SSH access run the following command replacing "/path/to/store" with the actual path to your store files and folders. SSH is faster and more reliable than FTP.
chmod -R 0777 /path/to/store
The auto upgrade tool should now work. After upgrade is complete set all files and folder back to "0755" excluding the following which need to remain writable listed below.