Coupon code not found OR not valid for this product. Please check the code and try again.

"Coupon code not found OR not valid for this product. Please check the code and try again". only occurs if the customer is not logged in or tries to use coupon as a guest. How can I fix?

PHP 5.3.3-7
joomla 2.5.17
VM 2.0.26a
AWO coupon 2.0.10 free

Hello,

In the free version, the customer is required to log in to use a coupon code, if one of the following exist when creating the coupon code:
- you have selected a specific customer
- you have set the number of uses PER CUSTOMER