Hi,
The payment links do now work for guests.
Of course, it's possible it doesn't work on your website because of some wrong configuration, or override.
For example, the payment link has to contain the "order_token" parameter which allows HikaShop to identify the user so that not anyone can access an order, only the person who created the order.
If that parameter is missing, then the link will be refused by HikaShop. This could happen if you have an old view override, or an old email override or an old version of HikaShop.
Alternatively, it could also be that the link generated uses a menu item that you configured to be accessible only for logged in users. In that case, the link will be refused by Joomla before even reasching HikaShop.
We would need more information on the situation to be able to say more on the problem.