Ok, so i see from the cart object file that you have set up the discount to apply if the promo code that is entered is:
WebAssist
testing your site and using the code "WebAssist" seams to work as intended, what promo cade are you testing with?
Note: PHP is case sensitive. "WebAssist" and "webassist" are not the same, make sure to use the correct case when entering the promo code.