Hi,
We fixed some elements in your configuration.
You "address state" custom fields was a "dropdown list" instead of a "zone" one ; so the address wasn't working properly (and because the taxes are link to the user address...)
After that, you are using "paypal express checkout" which is not really a payment method, so your checkout does not have a payment method selected and that's why you can't validate the "payment" step in your checkout workflow and go further.
Paypal express checkout is there to skip the HikaShop checkout and send the entire content of the cart to paypal and then create an order in HikaShop with the paypal callback.
If you want to use the HikaShop checkout workflow, you should add another payment method.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.