The application server could not be contacted

Hi, I have just downloaded Postgresql v11.1. and pgAdmin4 3.4  from postgresql.org for Windows 10.

I get an error message when starting pgAdmin 'The application server could not be contacted'

After searching around I find I can get round by running as administrator and deleting the contents of AppData/Roaming/pgAdmin but have to so this every time I start pgAdmin. Any suggestions please how I can get round this?

Thanks,

Carl