The HA network must be licensed in order to be used. For a basic installation, you will receive a license for five thin clients managed by the UMS so that you could carry out basic tests, e.g. with IGEL test setups. If you require licenses for further thin clients, please contact your IGEL reseller.
You should register the license file you receive in the UMS Console under UMS Administration > Global Configuration > Licenses > UMS Licenses.
An HA network only works with a license covering all managed thin clients registered to UMS. A mixed mode (devices with HA support and devices without HA support) is not possible.