Appointments plus plugin- calendar not updating

Hi There, I have recently purchased and installed your plugin onto a clients website in order to create a meeting room booking facility. The plugin for the most part has been exactly what we needed. However, on the booking page (created using the setting within the plugin), when a different service, or service provider is selected, the calendar does not update on clicking the availability button, and as such the correct availability and confirmation forms are not displaying. I am using the most recent version downloaded from your site (v1.5.5.1), and the site has very few other plugins installed (a contact form and multi language plugin).

Thanks in advance for your help.