Please follow up the steps below to fix this issue:
Download the Autorun.zip file from http://download.appeon.com/Autorun.zip, and then unzip it. After that please use this .exe file to replace the one under the directory of the Universal installation package.
Run the file Autorun.exe and provide us the screenshot of the first setup page.
The Install button shall appear on the screen that you posted here, below the View Readme button. If the problem persists even after you restart the computer and re-run the setup, please double check your environment against the PowerBuilder 2017 installation guide (https://www.appeon.com/system/files/product-manual/installation_guide_for_pb.pdf).