NI FI problems with postgree server

You will need to add permissions in postgres to allow connection for this user from the NiFi host.  You should follow documentation for your version of postgres to complete these steps.  If this is a sandbox, or dev setup, I recommend working to give the postgres user "wildcard" or unlimited access from any host.  This will remove the requirement of mapping the user permission to a specific host (whatever the nifi host is).  Once you get the user opened up you can try to test access from NiFi again.