Unable to book appointment from front end due to "no specific provider" working hours?


On my site http://www.thepreciousmettle.com.au/make-an-appointment-2/ I am seeing some odd behaviour with the Appointments+ plugin.

I have several services
Massage (30 min)
Massage (60 min) etc

and several providers with individual working hours
Jayne - Wed, Thur, Fri only

Bec - Mon -> Saturday

I have cofigured the two providers with the massage service.
Jayne Provider

Bec Provider

The plugin is configured to sync in both directions with google calendar and appears to be working. Creating appointments manually through the backend causes entries to be created in the google calendar, creating entries in the calendar and syncing through the backend causes the entries to be updated.

My issue appears to be related to working hours only.
If I set "No Specific Provider" to have NO working hours. I am unable to pick a massage appointment in the front end.

If I set "No Specific Provider" to have working days, then I am able to select those days from the front end.

The only change made between the two front end screen shots was the change in the "No Specific Provider" working hours.

Can you please tell me how I can get the calendar to work using the provider working hours, rather than the "No Specific Provider" working hours.

Kind regards,