The license server can be registered with XenDesktop either when XenDesktop is configured, or through the Change license server action on the Licensing node in Desktop Studio.
When the administrator specifies the address of the license server, Desktop Studio attempts to discover the License Configuration Service to allow more reading of license usage.
The error “Can’t get license info” appears if Desktop Studio cannot detect the License Configuration Service. The error does not signify that XenDesktop is not functioning as expected or that the users cannot connect to their desktops and applications.

For administrator authentication issues, only full administrators can connect to the License Configuration Service. Local administrators of the license server machine are implicitly full administrators of the License Configuration Service installed on that machine. Other full administrators can add the new administrators to the License Configuration service.

Some administrators setup on the License Configuration service might still experience problems when connecting to the service. This is generally because of the domain setup issues. The License Configuration Service uses Active Directory (AD) authentication to approve which users are allowed to retrieve license information. For this authentication process to work, either the license server must be in the same domain as the XenDesktop site, or there must be a two-way trust between both domains. Refer to Microsoft documentation for details on configuring trust relationships.

Complete the following tasks to re-validate a connection to the License Configuration Service:

1. Access the Licensing node in Desktop Studio.

2. Select Change Licensing Server.

3. Click Verify to refresh the licensing configuration information.

4. Click OK.

This forces the Desktop Delivery Controller to reconnect to the license server and validate the licensing information. It also adds all existing Desktop Studio administrators to the license configuration server to view the license use information.

To set up a full administrator on the License Configuration Service, use any of the following solutions to set up a new administrator.

Solution 1

Note: Administrators can be removed later after Desktop Studio is configured which is able to use the License Configuration Service.

Log on to the license server machine as an administrator and use the Computer Management Administrators tool to add the new administrator to the local Administrators security group.

Solution 2

1. Log on to the machine with Desktop Studio installed as the license server full administrator.

2. Run PowerShell.

3. Type Add-PSSnapin Citrix.LicensingConfig.Admin.V1.

Solution 3

1. Log on to the License server as full administrator.

2. Install LicensingConfig.PowerShellSnapIn.msi from the XenDesktop 5.1 iso, which can be found in either x64\Licensing or x86\ Licensing folder depending on whether your license server is 64-bit or 32-bit.

3. Run PowerShell.

4. Type Add-PSSnapin Citrix.LicensingConfig.Admin.V1.

Problem Cause

The possible causes for Desktop Studio not being able to detect the License Configuration Service are:

• The License Configuration Service is not running.

• The License Server VPX is in use.
  Though XenDesktop 5 Service Pack 1 through XenDesktop 5.6 are compatible with License Server VPX, the Desktop Studio cannot be used to view or manage licenses. Use the License Administration Console. Refer to Citrix Documentation - Other Known Issues and Considerations.

• The administrator who is using Desktop Studio does not have permission to access the License Configuration Service.

CTX133908 - Error: Detailed license information unavailable
Citrix Documentation - About Citrix Licensing