This installation Setup is only available and working for the following simulators:
Download Altitude here ➡️ https://www.ivao.aero/softdev/software/altitude.asp
Verify flight simulator is closed and Altitude UI or Core is not running either.
Uninstall all previous Altitude version(s).
The new Altitude installer is also able to remove previous versions upon startup:
Installation is very simple. Make sure your flight simulator is not running. Then unzip the downloaded setup file and run the setup program. This example shows FSX.