Calendar Dates not active

I have tested this out on my local host and everything is fine. But online I cannot get the Course Dates to go green.
Please see here: http://www.locums4care.co.uk/one-day-mandatory-training/
The client has not yet set up a Paypal account – is that the issue?
Do we need to have Woo Commerce Activated?
I just get a little warning sign and all dates are grey where 2nd and 8th September should be green.
Please help – I’ve been having a great deal of trouble finding the right Booking Calendar that links to paypal and this seems to be the best.

https://ww.wp.xz.cn/plugins/booking-system/