To activate the Transparent Database Engine:

In ISN, go to Settings --> Office Settings --> Payment Options:

Scroll down to eProcessingNetwork and activate this setting: 

Be sure to hit "Save" at the bottom of the page once you activate it.

Next, we need to make sure your EPN is setup to work under the TDBE:

Login to your eProcessingNetwork account here: https://www.eprocessingnetwork.com/msclogin.html

Next, navigate using the below screenshots: 

2. Ensure "TDBE (Transparent Database Engine)" is unchecked

3. Click "Save Disabled Integrations"

Once this is done, your ISN will process EPN transactions under EPN's native engine TDBE, which has better support for refund and void transactions.