Hi,
Please open a new thread when you have a new question.
With the checkout legacy setting turned off, you're using the new checkout of HikaShop, which is much better than the old one. So if that's ok with you, it's better to keep that option turned off.
The checkout not being accessible sometimes is because the business hours you configured. This option allows you to deactivate your checkout outside your business hours. So you want to not configure that option if you don't want to deactivate your checkout.
Also, when the checkout is deactivated, HikaShop displays an error message on the page, but it seems that your template isn't displaying the messages. I would recommend to check on that as it is important to let customers (and you) know when there is a problem :
www.hikashop.com/support/documentation/6...tibility-issues.html