Appointments+ Coupons has stopped working

Hi,

I have Appointments+ and MarketPress integrated - there are a few problems, but recently - last couple of days the Coupons has stopped working on the checkout.

Literally nothing happens when Apply is clicked.

To Reproduce ( You'll need to signup )

Add a rehearsal - http://www.silverstreetstudios.co.uk/my/store/products/rehearsal/

Then Checkout

At Cart you can try BOSSMAN100 - it's a 100% discount.

http://www.silverstreetstudios.co.uk/my/store/cart/

Thanks

Chris