I have been able to install the UE 4.20.1 but when I try to start it, the platform gets close. Is there any problem with my Mac Os version? It is a MacOs Sierra 10.12.6. May I download a previous version of UE 4 that is compatible with this version of MacOs?
What are your specs? Do they meet these requirements?
Have you tried re-verifying version 19 to make sure it was installed correctly?