If you encounter this error when installing or updating TSplus:

Download failed

Check your connection and click 'Retry' to try downloading the files again, or click 'Cancel' to terminate setup.

(Omniware is a rebranded version of TSplus - exact same code as TSplus)

Then you need to check this GPO and reboot the server:

Deploy a Group Policy Object to the client to turn off Automatic Root Certificates Update.
To do it, follow these steps on a Windows Server based server:

  1. Open Group Policy Management Console.
    To do it, hold the Windows key and press the r key.
    Type Gpmc.msc in the Run box, and then select OK.

  2. Create a new Group Policy Object (GPO)
    or select an existing Group Policy Object (GPO) to change.

  3. Right-click the selected Group Policy Object (GPO)
    and then select Edit and browse to the following Group Policy:

    Computer Configuration > Administrative Templates > System > Internet Communication Management > Internet Communication settings

  4. In the details pane,
    double-click Turn off Automatic Root Certificates Update, and then select Enabled.

Correcting this GPO allows AdminTool to be able to query TSplus servers.