Hi,
The problem comes from the URL parameters.
The way that the Joomla pagination works, it use the current url and submit a form to say that you want to change the page.
So, it will reload the current page and ask to display the page 2. But in your parameters, you forced some filters which are applied and put you in the first page (because potentially, some filters have changed).
If you apply the filters using the button "Find your Mattress!", you will have a clean url and you will be able to change the pagination.
So I will recommend you for the moment to redirect the user to the "short" url when giving some filters parameters. At this moment the parameters won't be in the url when changing the pagination.
I will create a bug issue in our tracker to fix in HikaShop as soon as possible.
There are several possible solution for this problem and I don't know which one the team will prefer.
But we will fix it.
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.