The Yoast SEO Premium plugin is not allowed to write to the custom redirect file located at /wp-content/uploads/wpseo-redirects/.redirects
Please make sure that the path and file are writeable by checking it over FTP. If the .redirects file is only writeable to the owner and you still get that error, you might need to change permissions on the file.
If you don』t know how to change permissions, please contact your web host for assistance.