Hi,
I tried to create an account in your website (using Chrome) and I didn't have your 500 error page.
Is your problem fixed ?
When you have 500 error page, please check your PHP error log to check if there is no PHP error which could generate this problem.
Otherwise, you can activate the Joomla debug mode in order to be informed if there is an error during a database query.
These will help us to understand the source of the problem and fix it.
But for the moment, I can't reproduce your problem in my side.
Kind 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.