While I was trying to update my themes and plugins to the latest WordPress version I have received the error : “Download failed. Failed to write request to temporary file”.
To fix this error you need to check different stuffs, below is the list:
1. Check if there is pace on the server or your cPanel account didn’t used all the space ( for me this fixed the error).
2. Check that the wp-content has the right permissions 755. If not give the permissions with chmod 755 wp-content
3. Check the upload file size. You can check it in media when you try to add a picture. In case it is 2MB it would be good to increase it to 20MB.
4. Edit the wp-config.php and add the line define(‘WP_TEMP_DIR’, ABSPATH . ‘wp-content/’); like in this tutorial: fix-download-failed-errors-on-update
After all are checked the problem should disappear and the plugins, themes or WordPress can be upgraded.