If you have manually installed the Trellix DLP extension in ePO - On-prem, you must also install the other extensions needed for Trellix DLP Network Prevent manually.
Download the extensions.
Install the Trellix DLP extension.
In ePO - On-prem, select Menu → Software → Extensions, then click Install Extension.
Follow these steps for each of the extensions. Install the extensions in this order:
Common UI package
Appliance Management Extension
Trellix DLP Appliance Management
Browse to the extension .zip file.
The installation dialog box displays the file parameters to verify that you are installing the correct extension.
Click OK twice.