We have user roles on our site that are either one week or one month in duration. We want to offer each of these for free to users with a special coupon. We set up the coupon, and set the discount at 100 (percent). Because the User must still register (using the Smith Registration Pro 3.31 module), they must enter their credit card info. The module shows their fee to be $0.

However, the transaction cannot be processed. The User receives an error "Auth: False"

Is the issue with the $0 transaction amount? Should we be using the TRIAL option, even though this is NOT a recurring billing?