Webform results don't download
I checked the permissions of the temporary files for our theme and sure enough, they were wrong. I am not sure what caused them to change, but they were set to root, whereas the dev site was set for www-data for both user and group. On our Debian server, Drupal uses the temporary files located at /tmp/example_theme. 

To fix:

sudo chown -R www-data /var/example_theme

sudo chgrp -R www-data /var/example_theme

That fixed this and many other problems we were having today.