It reports the app can't be opened, without further explanation, so I have no idea how to fix it.
Hi, I had the same issue, I put the app in the Application directory then I used a terminal to execute the following command :
sudo chmod -R 755 /Applications/The\ Past\ Within.app
then you enter your password (it's normal not to have any ***, when you type it)
Then you go to the finder and right-click on the app, then you maintain the "option" key of the keyboard when clicking on Open, to authorize an unknown developer.