welcome to the forum :)! Could you try to create an installation log file for us? To do that, first make a shortcut to the installer msi file. Then, right click on the shortcut and choose "Properties". In the properties window, add " /log log.txt" to the "Target"-path. The complete path should then look somewhat like that:
C:\Users\artoor\Downloads\Boxcryptor_v2.1.405.86_Setup.msi /log log.txt
Click "OK" and start the installation with this link. This will create a log.txt file in the same directory. Please send this file to firstname.lastname@example.org.