Appointment+ and password protected pages

The booking page is on a password protected page. Obviously the client has to have a password before they can use the system. However, when they enter the password the page is not revealed, it appears that the password did not work but if you leave the page or site and come back to it at a later date the booking page is visible.

This problem did not occur at the outset and yet I am not able to ascertain if it is a plugin conflict like super cache. There is also a url I see in the browser , bottom left of firefox, t. or i.skimresources does anyone know anything about it and is it a problem?
My URL is below with the password.

I should add that if I access a protected page without the plugin it works straightaway.