I’m running pgAdmin4 v3.0 and I’ve put localhost as host name.
I mean, left panel > servers > create > server and then connection tab > host name
I could not query tables, clicking on view/edit data > all rows had no results (nor error log entries).
After I changed server name from localhost to 127.0.0.1, all worked as expected!
I hope it helps, because I’ve lost so much time on this and could not find a proper answer.