While I have been successfully using MarketPress coupons prior to this last Upfront patch, now I do not receive any response when triggering the "Apply Coupon" button. I am able to access global functions such as mp_cart and marketpress.ajaxEvents but not mp_cart.applyCoupon.
There is no event listener registered for the button. I noticed another thread with a similar problem using the "Avada" theme, which I am not using nor familiar with. There are no related console errors nor PHP errors/warnings nor WP errors/warnings.
I have run a plugin test, enabled WP error logging, and neither of these yielded results. This seems to me to an issue with including the appropriate files (like mp_coupons.js) but I do not have extensive knowledge into how Marketpress is loaded. Access has been granted.