pgAdmin 4 Not connected to the server

I've installed Postgresql 11 and pgAdmin4 (version 4.5) and while I'm able to create tables in a new database, if I attempt to SELECT or INSERT into those tables I always get a message 'Not connected to the server or the connection to the server has been closed.' in the "Messages" tab in pgAdmin 4. If, however, I open the SQL Shell I can execute a SELECT on a table that I've attempted to insert into from pgAdmin and it shows that the rows have been inserted.