From v1.3.1, Splashtop Gateway supports offline license activation, which makes it easier when the Gateway is deployed inside a closed network. Please follow the instructions below.
Step 1. After finishing the Gateway installation and the OOBE process, go to System > License page, click Import Offline License button
Step 2. In the following page, click Save button to save the splashtop-activationid.txt file, and send it back to Splashtop Support at email@example.com or the sale representative you are contacting with Splashtop, Splashtop Support team will send back splashtop_on-prem_info.lic file for offline activation.
Import the activation file with the Open button, and activate.