It is not clear which part of the license system handles the end-user license and which part handles the demo license.
Having both TAC Vista and EcoStruxure Building Operation(EBO) installed on the same PC can cause conflicts in the license system.
EcoStruxure Building Operation
Building Operation Enterprise Server
If an EcoStruxure installation is only used for engineering and therefore will only have demo licenses activated, you don't need to install the license server. The service "FLEXnet Licensing Service" is installed by any EcoStruxure software package, and that is the service that will handle the activation of demo licenses.
If you will only use demo licenses on a PC and/or also have TAC Vista installed on the same PC, only install the license administrator and not the license server.
It is also possible to run TAC Vista and EBO using the same License server, please see Lesson Learned SmartStruxure license and TAC Vista license on the same PC