Hello,
You have a PHP fatal error.
So you have to get the corresponding PHP error message in order to understand what is the issue and know how to solve it.
As usual : PHP error log AND/OR set "error reporting level" to "maximum" in your Joomla global configuration.
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.