CSS Issue with MarketPress button

Hello, I am having an issue with the formatting of a button on my products page: http://procenter.staging.wpengine.com/courses/store/products/

The Add to Cart button has a green line on the top of it. It appears there are really 2 buttons on top of each other to give the Add to Cart button its function.

It seems that the .mp_button_addcart is formatted properly, but the button behind it, form.mp_buy_form has a green line that I can’t get rid of.

Can you please help me remove the line on top of this MarketPress button?

Thank you,