I'm sorry for the caused inconvenience.
In regard of the issue that JustDecompile is not running, can you please try to wipe all JustDecompile settings out and then try to run the tool again? All settings can be found here: %AppData%\JustDecompile (please delete everything in this folder).
If the suggested solution above doesn't work for you, please uninstall JustDecompile, delete all settings as described above, and then try to install JustDecompile using the MSI file again.
Please let us know if you still have issues running JustDecompile.