Coupon code is applied, but not saved in the table, prevented from generating reports

I’m placing an order in magento 1.9 and I’m using coupon, the coupon code used isn’t being saved in the coupon_code field of the sales_flat_order table, so I can’t issue the report. I performed a test manually entering the coupon code directly into the database and managed to generate the report. How can I check why the coupon doesn’t save on the table at the time of checkout?