Assuming installation completed with out errors and you are running Localizer as administrator, 3 things can prevent Localizer from operating correctly:
1. Licensing - you must have one, and only one license file in the Localizer folder, and it must be the correct hardware id.
2. Virtual comport driver is not correctly installed - use the device manager, select "show hidden devices" from the menu, then check "system devices" for the virtual serial port driver (Eltima)
3. No gps/gnss sensor - if Localizer cannot detect your GPS/GNSS sensor device because you don't have one, or the driver isn't registering it properly with windows, then Localizer won't work. If your sensor shows up in the device manager, you should be okay.
In all cases, Localizer will report issues in the Windows Application event log. It will generally give you very specific indications of what it thinks the problem is.