Hi Rohanmoola,
Sorry to hear you're having issues getting it to run. The Mac version of Reprisal Universe is a 32bit application and with recent changes latest versions of the Mac OS require 64bit applications.
Sadly due to the legacy software used to make Reprisal Universe I've currently been unable to successfully make a 64bit version.
Either you or I can contact itch to see if they can issue you a refund as there doesn't seem to be the tools to do so in the developer's control panel.