WP Smush It Pro "Request failed Site URL not accessible"

I have re-installed the WPMUDEV plugin & the WP Smush It Pro plugin on my wordpress website.
However when I click the "Send Smush Request" button I still get the message: "Request failed Site URL not accessible"
My API Key seems to be correct & connected.
I use http://www.shannonspetsitting.net/wp-login.php to login to my dashboard