Windows Defender SmartScreen is preventing the install from running.
When you attempt to install Process Server's Toolbox, you receive a warning titled "Windows protected your PC." To continue with the installation, click the "More Info" link located at the end of the warning message, then select "Run anyway."
User Account Control prompt
When you attempt to install Process Server's Toolbox, you receive the following prompt:
Do you want to allow the following program to make changes to this computer?
To continue with the installation, click "Yes."