Installation issue - not working at all on clean install


I purchased a subscription specifically to use the WHMCS WP integration plugin on a new site ( , the WHMCS is installed at , I have reinstalled everthing twice to clean installs but I still get an error message on the "welcome plugin" on my homepage that says "WHMCS Integration: couldn't connect to host", Im am using current versions of everything.

Have spend a day trying to get this plugin working, with minimal documentation. Not very impressed so far .

Can you please help.