We run an onlineshop and using your plugin too. Today customers told us they can't order anymore, the order-button disappear on checkout-site. Our checks in the log shows that all is working fine until update on 2.19.4 - a few days there are no other updates.
We tested now in the liveshop with old version 2.19.3 - all is working.
Then check in demo-shop with 2.19.4 - cart and checkout don't work.
We are using Woocommerce and some other plugins. It seems you've implemented in the new version something which is affecting our shop.
We never had such problems with your plugin - it's the first time.
We can't give more details information, we are no developers.