Plugin not working after Update

Hello,

After updating Woocommerce plugin to 3.0.3, our plugin which adds custom checkout fields is not working anymore. Can someone help?

Problem Site: http://dfp-dev.creativequoin.com/checkout
Working Site: http://dfp-test.creativequoin.com/checkout

Any help would be great. Thanks!