From Dahua Wiki
DSS License Activation
Step by Step Instruction
2. Click on Config.
3. Click on License.
4. Click on Activate License.
5. Enter the 16 digits license code that you received from Dahua. Then click on Activate now.
5. Your DSS Express is successfully activated, you will be able to see all available modules and license expiration.
Note: if it doesn't launch, you can type in http://DSS_IP_ADDRESS/admin/ on your web browser.
2. Login with credential that you setup when you first accessing Administrator Client.
3.Click on Activate License.
4. Click on Online Activate.
5. Enter the 16 digits license code that you received on the email.
6. Once code accepted, you will see prompt Activated Successfully.
7. On the Web Manager home screen, you can see the expiration date of your license.