This error message can occur when your merchant account's process mode is set to demo mode in the Blackbaud Payment Service Merchant Account section. 

To check the process mode of your merchant account:
  1. Click Revenue > Blackbaud Payment Service Merchant Accounts
  2. Click the drop down arrow next to your merchant account and click edit
  3. Make sure the process mode is set to Live if this is a live transaction
Make sure the proper merchant account is selected for your web forms: 
  1. Click Web > Web Payment Settings
  2. In the Payment Methods section make sure you're using the correct merchant account
  3. Click save after selecting the correct merchant account in the drop down menu