Sometimes WordPress runs into permission issues. Almost all the time, this is an issue that can only be handled at the server level. You can either contact your hosting provider to fix the issues or you can do it yourself. We recommend, if you do it yourself, you use SSH to do so. You will need SSH access to your server.
Navigate to your WordPress root and run the following commands. This will restore WordPress Folder and File permissions back to normal.
find . -type d -exec chmod 775 {} \;
find . -type f -exec chmod 664 {} \;