Why do I see the error 'weekday/weekend nightly breaks are not available' when making a reservation?

When setting up bookings, you need to ensure that all days are ticked within the Availability calendar to allow for guests to arrive on any day for their x-night stay. 

To do this, simply go to Edit Website Content > Availability and check the relevant Nightly Break Days. 

Nightly break days are only applicable if you allow your guests to book for just a one-night break, or a break over consecutive nights, but is something other than a weekly rate or a custom break type. 

Therefore, if you set up nightly break days in your system, you are allowing guests to book one or X number of consecutive nights, which the system will then calculate based on the nightly rate of the day that you've input.