I add the coupon code to the text field and submit, it shows the coupon was accepted.
Then I register the new user and hit submit.
Once I am redirected to the next page there is no difference in price and I have the option of moving along to buy with paypal but the price doesn't get changed.
The coupon I created had a 100% discount and is in the valid date range.
Thanks for the help, the plugin is great!