Following 2 GPOs should be configured for licensing server and license type for RDS.

Apply policy: Computer configuration>Windows component>Remote Desktop Services>Remote Desktop Session host>Licensing

1. Use the specified Remote Desktop License Server

2. Set the remote Desktop Licensing mode

Also, perform below steps to configure RDSH server:

Install Remote Desktop Licensing1)     In Server Manager, open the Manage menu and click Add Roles and Features.

2)     Click Next until you get to the Server Roles page. Check the box next to Remote Desktop Services and click Next.

3)     Click Next until you get to the Role Services page. Check the box next to Remote Desktop Licensing and click Next.

4)     Click Add Features if prompted.

5)     Then finish the wizard to install the role service.

Activate Remote Desktop Licensing1)     After RD Licensing is installed, in Server Manager, open the Tool menu, expand Terminal Services and click Remote Desktop Licensing Manager.

2)     The tool should find the local server. If it does not, right-click All servers, click Connect and type in the name of the local server. Once the local server can be seen in the list, right-click the server and click Activate Server.

3)     In the Welcome to the Activate Server Wizard page, click Next.

4)     In the Connection Method page, click Next.

5)     In the Company Information page, enter the required information and click Next.

6)     All the fields on the Company Information page are optional so you do not have to enter anything. Click Next.

7)     In the Completing the Activate Server Wizard page, uncheck the box next to Start Install Licenses Wizard now and click Finish. Since the session hosts will be configured to pull Per User licenses, there is no need to install licenses on the RD Licensing Server.

8)     In RD Licensing Manager, right-click the server and click Review Configuration.

9)     Ensure you have green check marks. If the person installing Remote Desktop Licensing does not have permissions to add the server to the Terminal Server License Servers group in Active Directory, ask a domain admin to do it manually. If you have the proper permissions, click Add to Group.

10)     Click Continue when prompted that you must have Domain Admins privileges.

11)  Click OK when prompted that the computer account has been added.

12)  Click OK to close the window.

Remote Desktop Licensing ConfigurationDo the following on your 2012 R2 Remote Desktop Session Hosts. The only way to configure Remote Desktop Licensing is using group policy (local or domain).

1)     For local group policy, run gpedit.msc.

2)     Go to Computer Configuration > Administrative Templates > Windows Components > Remote Desktop Services > Remote Desktop Session Host > Licensing.

3)     Double-click Use the specified Remote Desktop license servers. Change it to Enabled and enter the names of the XenDesktop Controllers. Click OK.

4)     Double-click Set the Remote Desktop licensing mode. Change it to Enabled and select Per User. Click OK.

5)     In Server Manager, open the Tools menu, expand Terminal Services and click RD Licensing Diagnoser.

6)     The Diagnoser should find the license server and indicate the licensing mode. It’s OK if there are no licenses installed on the Remote Desktop License Server.

NOTE: The group policy should point to your RD licensing servers. if you installed it on your Controllers then you would specify them. Otherwise specify the RD Licensing server names.

Source

Technically, Citrix applications will still work if VDA is pointed to an empty RDS license server. When Admins login to the VDA through RDP, it will throw some errors. But Citrix says we should have RDS license server with user/device cals.