I have installed PostgreSQL 9.6.2 on my Windows 8.1. But the pgadmin4 is not able to contact the local server. I have tried several solutions suggested here in stackoverflow
I had the same issue on the macosx and I renamed .pgadmin (in /users/costa) to .pgadminx and I was able to start pgAdmin4.
macosx
.pgadmin (in /users/costa) to .pgadminx
pgAdmin4